CN107111239A - Method and Apparatus Using Patterning Device Topography-Introduced Phase - Google Patents

Abstract

One method comprises the following steps: measuring a three-dimensional topography of features of a pattern of a lithographic patterning device; and calculating wavefront phase information resulting from the three-dimensional topography of the pattern from the measurements.

Description

Method and Apparatus Using Patterning Device Topography-Introduced Phase

Cross References to Related Applications

This application claims priority to US Application 62/093,363, filed December 17, 2014, which is hereby incorporated by reference in its entirety.

technical field

The present invention relates to methods and apparatus for using phase introduced by a patterning device, for example, in the optimization of a pattern of a patterning device and one or more illumination properties of a patterning device, on a patterning device In the design and/or in computational lithography of one or more structural layers.

Background technique

A lithographic apparatus is a machine that applies a desired pattern to a substrate, usually a target portion of the substrate. For example, lithographic equipment may be used in the manufacture of integrated circuits (ICs). In this case, a patterning device, alternatively referred to as a mask or reticle, may be used to generate the circuit pattern to be formed on the individual layers of the IC. The pattern can be transferred onto a target portion (eg, comprising a portion, one or more dies) on a substrate (eg, a silicon wafer). Transfer of the pattern is usually achieved by imaging the pattern onto a layer of radiation sensitive material (resist) provided on the substrate. Typically, a single substrate will contain a network of successively patterned adjacent target portions. Known lithographic apparatuses include: so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once; and so-called scanners, in which In , each target portion is irradiated by scanning the pattern with a radiation beam in a given direction ("scanning" direction) while simultaneously scanning the substrate synchronously in a direction parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

Contents of the invention

The patterning device used to pattern the radiation, such as a mask or reticle, may produce undesired phase effects. In particular, the topography of the patterning device (e.g., the variation in the topography of features of a pattern on the patterning device from the nominal topography of the features) may introduce undesirable phase shifts into the patterned radiation (e.g., introducing into the diffraction orders emanating from the features of the patterning device's pattern). This phase shift may reduce the accuracy with which the pattern is projected onto the substrate.

The present description relates to methods and apparatus for using phase introduced by a patterning device, such as for use on a patterning device in the optimization of a pattern of a patterning device and one or more illumination properties of a patterning device In the design and/or in computational lithography of one or more structural layers.

In one aspect, a method is provided that includes measuring a three-dimensional topography of a feature of a pattern of a lithographic patterning device and calculating wavefront phase information resulting from the three-dimensional topography of the pattern from the measurement results.

In one aspect, there is provided a method of fabricating a device wherein a device pattern is applied to a series of substrates using a photolithographic process, the method comprising using the methods described herein to prepare the device pattern and exposing the device pattern to the substrate superior.

In one aspect, there is provided a non-volatile computer program product comprising machine readable instructions configured to cause a processor to perform the methods described herein.

Description of drawings

Embodiments are described herein, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 schematically shows an embodiment of a lithographic apparatus;

Figure 2 schematically shows an embodiment of a photolithography unit or cluster (cluster);

Figure 3 schematically illustrates diffraction of radiation by a patterning device;

4A-4E are simulated phase diagrams of different diffraction orders for patterns of a patterning device illuminated at normal incidence angles for various pitches;

Figure 5 is a simulated phase diagram of various diffraction orders for patterns of a patterning device illuminated at various angles of incidence;

6A is a schematic diagram of a functional module for simulating a device manufacturing process;

Figure 6B is a flowchart of a method according to an embodiment of the invention;

Figure 7 is a flowchart of a method according to an embodiment of the present invention;

Figure 8A is a graph of simulated diffraction efficiencies for various diffraction orders of patterns of a patterning device at two different absorber thicknesses;

Figure 8B is a graph of the simulated patterning device's topography-induced phase (wavefront phase) for various diffraction orders of the patterning device's pattern at two different absorber thicknesses;

Figure 9A is a graph of the simulated patterning device's topography-induced phase (wavefront phase) for various diffraction orders of a binary mask;

9B is a graph of the topography-induced phase (wavefront phase) of a simulated patterning device for various absorber thicknesses of a binary mask;

Figure 10A is a graph of the topography-induced phase (wavefront phase) of a simulated patterning device for various diffraction orders for a phase shift mask;

Figure 10B is a graph of topography-induced phase range values (wavefront phase) for a simulated patterning device for various absorber thicknesses for a phase shift mask;

Figure 11 is a graph of simulated best focus difference for phase shift masks for various pitches;

12A is a graph of the topography-induced phase (wavefront phase) of a simulated patterning device for various diffraction orders for a binary mask illuminated at various illumination incidence angles;

12B is a graph of the topography-induced phase (wavefront phase) of a simulated patterning device for various diffraction orders for a phase-shift mask illuminated at various illumination incidence angles;

Figure 13A is a graph of measured dose sensitivity for various best focus values for a binary mask;

Figure 13B is a graph of measured dose sensitivity for various best focus values for a phase shift mask;

14A is a graph of the topography-induced phase (wavefront) of the simulated patterning device for various diffraction orders for the vertical feature of the EUV patterning device at zero angle of incidence relative to the chief ray at a non-zero angle of incidence. Phase) chart;

Figure 14B is a graph of the topography-induced phase (wavefront) of the simulated patterning device for various diffraction orders for the horizontal characteristics of the EUV patterning device at a non-zero angle of incidence relative to the chief ray at the non-zero angle of incidence. Phase) chart;

15A is a graph of simulated patterning device topography-induced phase (wavefront phase) for various diffraction orders of an EUV mask for vertical features at various angles of incidence;

15B is a graph of simulated patterning device topography-induced phase (wavefront phase) for various diffraction orders of an EUV mask for horizontal features at various angles of incidence;

Figure 16 shows coherence versus simulated modulation transfer function (MTF) for various line and space patterns for an EUV patterning device illuminated with bipolar illumination;

Figure 17 schematically illustrates an embodiment of a scatterometer;

Figure 18 schematically illustrates another embodiment of a scatterometer;

Fig. 19 schematically shows the outline of a measurement spot on a substrate and the form of a multi-grating target.

detailed description

Before describing the embodiments in detail, it is instructive to provide an example environment in which the embodiments may be implemented.

Figure 1 schematically shows a lithographic apparatus LA. The equipment includes:

an illumination system (illuminator) IL configured to condition a radiation beam B (eg, DUV radiation or EUV radiation);

a support structure (e.g. a mask table) MT configured to support a patterning device (e.g. a mask) MA and connected to a first positioning device PM configured to precisely position the patterning device according to specified parameters;

a substrate table (e.g. a wafer table) WTa configured to hold a substrate (e.g. a resist-coated wafer) W and associated with a second positioning device configured to precisely position the substrate according to specified parameters PW connected; and

a projection system (e.g. a refractive projection lens system) PS configured for projecting the pattern imparted to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (e.g. comprising one or more dies) .

The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, to direct, shape, or control the radiation.

The patterning device support structure holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions such as, for example, whether the patterning device is held in a vacuum environment. The patterning device support structure may employ mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The patterning device support structure may be a frame or a table, for example, which may be fixed or movable as desired. The patterning device support structure can secure the patterning device in a desired position (eg relative to the projection system). Any use of the terms "reticle" or "mask" herein may be considered synonymous with the more general term "patterning device."

The term "patterning device" as used herein should be broadly construed to mean any device that can be used to impart a radiation beam with a pattern in its cross-section so as to form a pattern in a target portion of a substrate. It should be noted that the pattern imparted to the radiation beam may not correspond exactly to the desired pattern on the target portion of the substrate (eg if the pattern includes phase shifting features or so called assist features). Typically, the pattern imparted to the radiation beam will correspond to a specific functional layer in a device formed on the target portion, such as an integrated circuit.

The patterning device can be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography and include mask types such as binary, alternating phase-shift, attenuated phase-shift, and various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be independently tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern to the radiation beam reflected by the mirror matrix.

The term "projection system" as used herein may be broadly interpreted to include any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic, and electrostatic optical systems, or any combination thereof, as for all as appropriate for the exposure radiation used, or for other factors such as the use of immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system".

As shown here, the device is transmissive (eg, employs a transmissive mask). Alternatively, the device may be reflective (eg, employing a programmable mirror array of the type described above, or employing a reflective mask).

The lithographic apparatus can be of the type with two (dual stage) or more stages (e.g., two or more substrate stages, two or more patterning device support structures, or a substrate stage and a metrology stage) . In such "multi-stage" machines, additional tables may be used in parallel, or one or more other tables may be used for exposure while preparatory steps are being performed on one or more tables.

The lithographic apparatus may also be of the type in which at least a part of the substrate may be covered by a liquid having a relatively high refractive index, such as water, in order to fill the space between the projection system and the substrate. The immersion liquid can also be applied to other spaces in the lithographic apparatus, such as the space between the mask and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term "immersion" as used herein does not mean that the structure (such as a substrate) must be immersed in a liquid, but only that the liquid is located between the projection system and the substrate during exposure.

Referring to FIG. 1 , an illuminator IL receives a radiation beam from a radiation source SO. The source and lithographic apparatus may be separate entities (eg when the source is an excimer laser). In this case, the source is not considered to form part of the lithographic apparatus, and the radiation beam is diverted from the The source SO is passed to the illuminator IL. In other cases, the source may be an integral part of the lithographic apparatus (eg when the source is a mercury lamp). The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

The illuminator IL may comprise an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in the pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a concentrator CO. The illuminator can be used to condition the radiation beam to have a desired uniformity and intensity distribution in its cross-section.

The radiation beam B is incident on the patterning device (eg mask) MA held on a patterning device support (eg mask table MT) and is patterned by the patterning device. After having passed through the patterning device (eg mask) MA, the radiation beam B passes through a projection system PS which focuses the radiation beam onto a target portion C of the substrate W. With the help of a second positioner PW and a position sensor IF (for example, an interferometric device, a linear encoder, a two-dimensional encoder or a capacitive sensor), the substrate table WTa can be moved precisely, for example in order to place different target parts C is positioned in the path of said radiation beam B. Similarly, the first positioner PM and a further position sensor (not explicitly shown in FIG. The path of beam B precisely positions patterning device (eg, mask) MA. Typically movement of the patterning device support (eg mask table) MT can be achieved with the aid of a long stroke module (coarse positioning) and a short stroke module (fine positioning) forming part of said first positioner PM. Similarly, movement of the substrate table WTa may be achieved using a long-stroke module and a short-stroke module forming part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the patterning device support (eg mask table) MT may only be associated with a short-stroke actuator, or may be fixed.

Patterning device (eg mask) MA and substrate W may be aligned using mask alignment marks M1 , M2 and substrate alignment marks P1 , P2 . Although the substrate alignment marks are shown occupying dedicated target portions, they may be located in spaces between target portions (these are known as scribe line alignment marks). Similarly, where more than one die is disposed on the patterning device (eg mask) MA, the mask alignment marks may be located between the dies. Small alignment marks may also be included within the die, between device features, in which case it is desirable that the marks be as small as possible and not require any different imaging or process conditions than adjacent features. An alignment system that detects alignment marks will be described further below.

The described device can be used in at least one of the following modes:

In step mode, the entire pattern imparted to the radiation beam is projected onto the target portion C in one pass while the patterning device support (e.g., mask table) MT and substrate table WTa are held substantially stationary ( That is, a single static exposure). The substrate table WTa is then moved in the X and/or Y direction so that different target portions C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

In scanning mode, the pattern imparted to the radiation beam is projected onto a target portion C (i.e., a single dynamic exposure). The velocity and direction of the substrate table WTa relative to the patterning device support (eg mask table) MT can be determined by the (de-)magnification and image inversion characteristics of the projection system PS. In scanning mode, the maximum size of the exposure field limits the width of the target portion in a single dynamic exposure (in the non-scanning direction), while the length of the scanning movement determines the height of the target portion (in the scanning direction). ).

In another mode, the patterning device support (e.g., mask table) MT holding the programmable patterning device is held substantially stationary and the pattern imparted to the radiation beam is projected onto the target portion C At the same time, the substrate table WTa is moved or scanned. In this mode, a pulsed radiation source is typically employed and the programmable patterning device is updated as required after each movement of the substrate table WTa, or between successive radiation pulses during scanning. This mode of operation is readily applicable in maskless lithography using programmable patterning devices, such as programmable mirror arrays of the type described above.

Combinations and/or variations of the above described modes of use, or entirely different modes of use may also be employed.

The lithographic apparatus LA is of the so-called dual-stage type, which has two tables WTa, WTb (e.g. two substrate tables) and two stations - an exposure station and a measurement station, between which the stations can be swapped. For example, while one substrate on one stage is being exposed at the exposure station, another substrate may be loaded onto another substrate stage at the measurement station and various preparatory steps performed. Said preliminary steps may include mapping the surface control of the substrate with a level sensor LS and measuring the position of alignment marks on the substrate with an alignment sensor AS, both supported by a reference frame RF. If the position sensor IF is unable to measure the position of the table when it is at the measurement station as well as at the exposure station, a second position sensor may be provided to enable the position of the table to be tracked at both stations. As another example, while a substrate on one station is being exposed at an exposure station, another station without a substrate waits at a measurement station (where measurement activity may optionally take place). This additional station has one or more measuring devices and may optionally have other tools (eg cleaning equipment). When a substrate has been exposed, the stage without the substrate moves to the exposure station to perform e.g. measurements, and the stage with the substrate moves to a position where the substrate is unloaded and another substrate is loaded (e.g., measurement stand). These multi-table arrangements can achieve a substantial increase in the productivity of the device.

As shown in FIG. 2, the lithographic apparatus LA may form part of a lithographic cell LC (sometimes referred to as a lithocell or a lithocluster) which also includes components for performing one or more processes on a substrate. Equipment for pre-exposure and post-exposure processing. Typically, these devices include one or more spin coaters SC to deposit the resist layer, one or more developers DE to develop the exposed resist, one or more chill plates CH and one or more baking sheets BK. A substrate handler or robot RO picks up the substrate from the input/output ports I/O1, I/O2, then moves it between different processing devices, and then transfers it to the feed table LB of the lithographic apparatus. These devices, often collectively referred to as a track, are under the control of a track control unit TCU which itself is controlled by a supervisory control system SCS which also controls the lithographic apparatus via the lithographic control unit LACU. Accordingly, different devices can be operated to maximize productivity and process efficiency.

In order for a substrate exposed by a lithographic apparatus to be properly and consistently exposed, the exposed substrate needs to be inspected to measure one or more properties such as overlay error between successive layers, line thickness, critical dimension (CD), etc. . If an error is detected, adjustments may be made to the exposure of one or more subsequent substrates. This may be especially useful, for example, where the inspection can be done quickly and quickly enough that another substrate of the same batch is still to be exposed. In addition, substrates that have been exposed can also be stripped and reprocessed (to increase yield), or can be discarded, thereby avoiding exposure on substrates known to be defective. In case only some target portions of the substrate are defective, only those target portions that are intact can be further exposed. Another possibility is to use a setting of a subsequent process step to compensate for the error, eg the timing of the trim etch step can be adjusted to compensate for the substrate-to-substrate CD variation resulting from the lithography process step.

The inspection apparatus is used to determine one or more properties of a substrate, and in particular, to determine how one or more properties of different substrates or different layers of the same substrate vary from layer to layer and/or across the entire substrate Bottom change. The inspection apparatus may be integrated into the lithographic apparatus LA or the lithographic cell LC, or may be a stand-alone device. In order to be able to make the most rapid measurements, it is desirable for the inspection equipment to measure one or more properties in the exposed resist layer immediately after exposure. However, latent images in resists have very low contrast (only a small difference in refractive index between parts of the resist exposed to radiation and parts of the resist not exposed to radiation), and not all The inspection equipment has sufficient sensitivity for effective measurement of the latent image. Therefore, measurements can be made after the post-exposure bake step (PEB), which is usually the first step performed on an exposed substrate and increases the exposed and unexposed The contrast between the parts. At this stage, the image in the resist can be said to be semi-latent. The developed resist image can also be measured at points where exposed or non-exposed portions of the resist have been removed, or after a pattern transfer step such as etching. The latter possibility limits the possibility of reworking defective substrates, but may still provide useful information, eg for process control purposes.

Fig. 3 schematically shows a cross-sectional view of a part of a patterning device MA, such as a mask or a reticle. The patterning device MA includes a substrate 300 and an absorber 302 . The substrate 1 may eg be formed of glass or any other suitable material substantially transparent to the radiation beam B of the lithographic apparatus, eg DUV radiation. Although embodiments are described with respect to transmissive patterning devices (ie, patterning devices that transmit radiation), embodiments may be applied to reflective patterning devices (ie, patterning devices that reflect radiation). In embodiments where the patterning device is a reflective patterning device, the patterning device may be arranged such that the radiation beam is incident on the absorber and the gap between the absorbers, then passes through the gap, and optionally through the absorbing body to be incident on a reflector located behind the gap (and optionally behind the absorber).

The material of the absorber 302 may for example be molybdenum silicide (MoSi) or any other suitable material which absorbs the radiation beam B of the lithographic apparatus (for example DUV radiation), i.e. the absorbing material blocks the radiation beam or when the radiation beam passes through the absorbing material A portion of the radiation beam B is absorbed. A patterning device with an absorbing material that blocks the radiation beam may be referred to as a binary patterning device. The MoSi can be provided with one or more dopants which can change the refractive index of the MoSi. The radiation does not have to travel through the absorber material 302 , and for some absorber materials 302 substantially all of the radiation may be absorbed in the absorber material 302 .

The absorber 302 does not completely cover the substrate 300, but is configured in an arrangement, ie a pattern. A gap 304 then exists between regions of the absorber 302 . As mentioned, Figure 3 shows only a small part of the patterning device MA. In practice, the absorbers 302 and gaps 304 are arranged to form an arrangement that may have, for example, thousands or millions of features.

A radiation beam B (see FIG. 1 ) of the lithographic apparatus is incident on the patterning device MA. Radiation beam B is initially incident on and passes through substrate 300 . The radiation beam is then incident on absorber 302 and gap 304 . Radiation incident on the absorber 302 passes through the absorber but is partially absorbed by the absorbing material. Alternatively, the radiation is substantially completely absorbed in the absorber 302 and substantially no radiation is transmitted through the absorber 302 . Radiation incident on gap 304 passes through the gap without being substantially or partially absorbed. The patterning device MA then applies a pattern to the radiation beam B (the pattern may be applied to a non-patterned radiation beam B or to an already patterned radiation beam B).

As further shown in FIG. 3 , as the radiation beam B passes through the gap 304 (and optionally through the absorber 302 ), the radiation beam B is diffracted into various diffraction orders. In Fig. 3, the 0, +1, -1, +2 and -2 diffraction orders are shown. However, it should be understood that there may be more, higher or fewer diffraction orders. The size of the arrows associated with the diffraction orders primarily indicates the relative intensities of the diffraction orders, ie, the 0th diffraction order is more intense than the −1 and +1 diffraction orders. However, note that these arrows are not to scale. Furthermore, it should be understood that not all diffraction orders may be captured by the projection system PS, depending eg on the numerical aperture of the projection system PS and the angle of incidence of the illumination onto the patterning device.

Furthermore, in addition to the intensity, the diffraction order also has a phase. As noted above, the topography of the patterning device MA (eg, the ideal pattern features themselves, unevennesses on the pattern surface of the patterning device, etc.) may introduce undesirable phases into the patterned radiation beam.

This phase can cause, for example, focus position differences and image shifts. Focus differences arise when the radiation beam is subjected to even order aberrations, for example caused by the topography of the patterning device. That is, "even" means that the phase of the -nth diffraction order and the corresponding +nth diffraction order are approximately the same. When the radiation beam is subjected to even order aberrations, the pattern image can be shifted in a direction transverse to the optical axis of the lithographic apparatus. That is, "odd" means that the phase of the -nth diffraction order and the phase of the corresponding +nth diffraction order have substantially the same magnitude, but opposite signs. This lateral movement may be referred to as image shift. Image shifting may result in loss of contrast, pattern asymmetry, and/or positioning errors (eg, the pattern is shifted horizontally from a desired position which may result in overlay errors). In general, then, the phase of a diffraction order can be decomposed into an even phase component and an odd phase component, where an even phase distribution will usually be entirely an even phase component and an odd phase distribution will generally be either an entirely odd phase component or an odd phase component with an even phase component. A combination of phase components.

Poor focus, image shift, loss of contrast, etc. may degrade the accuracy of the pattern projected by the lithographic apparatus onto the substrate. Accordingly, embodiments described herein may reduce focus differences, image shift, contrast loss, and the like.

In particular, the phase and intensity introduced by the topography of the patterning device as described above are wavefront phase and intensity, respectively. That is, the phase and intensity are in the diffraction order at the pupil and are set by all absorbers. As mentioned above, such wavefront phase and intensity may cause, for example, poor focus and/or loss of contrast.

This wavefront phase is distinct from the intentional phase shift effect at the image plane (ie substrate level) provided by a patterning device (eg a phase shift mask) designed to create this phase shift. Then, unlike the wavefront phase, the phase shift effect usually exists for only some absorbers and causes the phase of the electric field to change. For example, in embodiments where the radiation beam is partially absorbed by an absorber of the patterning device, as the radiation beam exits the absorber, a phase shift of the radiation beam may arise between the radiation and radiation passing through an adjacent gap. Rather than causing a loss of contrast, the phase shift effect desirably increases the contrast of aerial images formed using the patterning device. The contrast can be at its maximum, for example, when the phase of the radiation that has passed through the absorber differs by 90 degrees from the phase of the radiation that has not passed through the absorber.

Thus, in embodiments, the use of topography-introduced phase and/or intensity (wavefront phase and/or intensity) information (whether in data form, or in the form of a mathematical description, etc.) of a patterning device is discussed herein. various techniques. In one embodiment, the phase introduced by the topography of the patterning device (wavefront phase) is used for correction to reduce the effect of this phase. In an embodiment, such correction involves (re)designing the topography of the patterning device to reduce or minimize the influence of the phase (wavefront phase) introduced by the topography of the patterning device. For example, a stack of patterning devices (e.g., one or more elements/layers making up the patterning device and/or a process for making these one or more elements/layers) is defined according to, for example, refractive index, extinction coefficient, sidewall corners, feature widths, pitches, thicknesses, and/or parameters of a layer stack (e.g., composition of the stack, order of layers in the stack, etc.) Phase (wavefront phase) effect. In one embodiment, such corrections involve applying corrections to one or more lithographic apparatus parameters (e.g., illumination mode, numerical aperture, phase, magnification, etc.) to reduce or minimize the shape of the patterning device. The influence of the phase (wavefront phase) introduced by the appearance. For example, the compensation phase may be introduced downstream of the patterning device, eg in a projection system of a lithographic apparatus. In one embodiment, such corrections involve a modification of the patterning device's pattern and/or one or more illumination parameters (commonly referred to as the illumination pattern and typically including radiation-related parameters) applied to the patterning device by the lithographic apparatus. Information on the type and details of the intensity distribution, eg whether it is annular illumination, dipole illumination, quadrupole illumination, etc.) to reduce or minimize the influence of phase (wavefront phase) introduced by the topography of the patterning device.

In another embodiment, the topography-induced phase of the patterning device (wavefront phase) is used in computational lithography calculations. In other words, the topography-induced phase of the patterning device (wavefront phase) and optionally the topography-induced intensity of the patterning device (wavefront intensity) is introduced into the simulation/ in the mathematical model. Thus, instead of or in addition to the physical dimensional description of the patterning device's topography for such simulations/mathematical models, the patterning device's topography-induced phase and optionally the patterning device's topography-induced intensity are used in These simulations/mathematical models are used to generate eg simulated space images.

Therefore, for these applications, a topography-induced phase (wavefront phase) of the patterning device is required. To obtain the wavefront intensity and phase of a pattern or a feature of the pattern, the pattern or feature can be programmed into a lithography simulation tool, such as Hyperlith software, available from Panoramic Technology, Inc. The simulator can strictly compute a near-field image of the pattern or feature. This calculation can be done by Rigorous Coupled Wave Analysis (RCWA). The Fourier transform can be used to generate intensity and phase values for the diffraction orders. These scattering coefficients can then be analyzed to determine corrections that can be applied to remove or improve the phase. In particular, the analysis can focus on the magnitude of the phase, eg the range of phase across diffraction orders. In an embodiment, the correction is applied to reduce the magnitude of this phase and in particular to reduce the magnitude of the phase range across the diffraction orders.

The analysis may focus on a "fingerprint" of phase and/or intensity across diffraction orders. For example, the analysis can determine whether the phase distribution is substantially even across diffraction orders, such as substantially symmetric with respect to, for example, the 0th order. As another example, the analysis might determine whether the phase distribution is substantially odd across diffraction orders, such as substantially asymmetric with respect to, for example, the 0th order. Where the phase distribution is substantially odd across diffraction orders, as described above, the phase distribution may be a combination of odd and even phase components. In both cases, patterns or contours with the same shape as the "signature" of the phase can be identified. In one embodiment, such patterns or profiles are described by a suitable set of basis or eigenfunctions. The suitability of this basis or characteristic function may depend on the suitability of the function used in the lithographic apparatus or on the phase range in which the main phase variation can be described. In one embodiment, this pattern or profile is described by a set of polynomial functions that are orthogonal on the interior of a circle. In an embodiment, such patterns or profiles are described by Zernike polynomials (with Zernike coefficients), by Bessel functions, Mueller matrices or Jones matrices. Zernike polynomials can be used to apply a suitable correction to this phase that will reduce or eliminate the undesired phase. For example, Zernike polynomials with m=0 cause spherical aberration/correction. They then cause a feature-dependent focus shift of the image plane. Zernike polynomials with M=2 cause astigmatism/correction. Zernike polynomials with M=1 and m=3 are called coma and 3-foil, respectively. These cause offsets and asymmetries of the image pattern in the x-y image plane.

Referring to FIGS. 4A-4E , there are shown simulated patterning device topography for diffraction orders exposed to 40 nm lines of a thin binary mask at various pitches using normal incident illumination of 193 nm with a numerical aperture of 1.35. Graph of incoming phase (wavefront phase). The graph shows simulation results that measure how the phase of the wavefront varies as a function of diffraction order. This simulation models the projection of the mask pattern when exposed to the 193 nm illumination and can be implemented using, for example, Hyperlith software, available from Panoramic Technology, Inc. The phase is in radians, and for diffraction orders, 0 corresponds to the 0th diffraction order, where Figures 4A-D represent the scattering order as an integer (m) and Figure 4E represents the scattering order normalized with respect to the pitch ( m/pitch). The simulations were performed for patterns with four different pitches, namely 80 nm (FIG. 4A), 90 nm (FIG. 4B), 180 nm (FIG. 4C) and 400 nm (FIG. 4D). As usual, the pitch dimension is the pitch at the substrate side of the projection system PS of the lithographic apparatus (see Fig. 1). Figure 4E shows a combination of data points for the graphs for 80nm, 90nm and 400nm when the diffraction orders are normalized with respect to the pitch.

Referring to Figures 4A and 4B, the phase distribution is even. Also, it is observed that the phase has a pattern. For example, it can generally be described by the Zernike term Z4 (ie Noll index 4). Referring to FIG. 4C , the phase distribution is even, patterned and can be generally described by the Zernike term Z9 (ie, Noel index 9). Referring to FIG. 4D , the phase distribution is even, has a pattern and can generally be described by a higher order Zernike term, such as the Zernike term Z25 (ie, Noel index 25). Referring to Figure 4D, a combination of data points for the charts for 80nm, 90nm and 400nm is shown. It can be seen that the data points are all generally arranged along the "curve" of the 400nm graph. Accordingly, specific patterns, such as higher order Zernike terms, such as the Zernike term Z25 (ie Knoll index 25), can be applied to the pitch range. The phase is then not highly pitch dependent, so phase corrections can be applied to pitch ranges using eg particularly high order Zernike terms, eg Zernike terms Z25 (ie Noir index 25).

Thus, for normal incidence, the phase distribution is usually even and results in a loss of optimum focus. In turn, the phase has a pattern which can typically be defined by a Zernike term Z4 (i.e. Noll index 4), a Zernike term Z9 (i.e. Noll index 9) and/or a higher order Zernike term such as Zernike polynomials of the Zernike term Z25 (ie, Noel index 25) to describe. Such a description of the pattern of phases may eg be used to make corrections as discussed further.

Referring to FIG. 5 , there is shown a patterning device for a simulation of diffraction orders exposed to a mask by 193 nm illumination at various angles of incidence for 40 nm lines of a thin binary mask at a pitch of 400 nm using a numerical aperture of 1.35. A graph of the phase (wavefront phase) introduced by the topography. The graph shows simulation results that measure how the phase of the wavefront varies as a function of diffraction order. This simulation models the projection of the mask pattern when exposed to the 193 nm illumination and can be implemented using, for example, Hyperlith software. The phase is in radians, and the diffraction order is an integer, with 0 corresponding to the 0th diffraction order. The simulations were performed for illumination with a σ(sigma) of -0.9 corresponding to an incident angle of -16.5 degrees, a σ of 0 corresponding to an incident angle of 0 degrees, and a σ of 0.9 corresponding to an incident angle of 16.5 degrees.

Referring to Fig. 5, for σ of 0, the phase distribution is even (as shown in Fig. 4A-E), and can usually be described by a higher-order Zernike term, such as the Zernike term Z25 (i.e., Noel index 25) . However, for σ of -0.9, the phase distribution has additional odd components and can be described by one or more odd terms on their own or in addition to the even terms by one or more odd terms Described, for example, by Zernike term Z3 (ie, Noll index (Noll index) 3) or Zernike term Z7 (ie, Noll index 7). Similarly, for σ of 0.9, the phase distribution has additional odd components and can be described by one or more odd terms on their own or by one or more odd terms in addition to the even terms Described, for example, by Zernike term Z3 (ie, Noel index 3) or Zernike term Z7 (ie, Noel index 7). Thus, if image formation involves multiple angles of incidence and the odd phase portion is different for each angle of incidence, image shift (resulting in loss of contrast, pattern positioning errors, etc.) occurs. Contrast loss and pattern positioning errors are significant parameters for lithography optimization and design, and thus identification and use of this phase effect can be used to reduce or minimize contrast loss and pattern positioning errors.

Similar to the angle of incidence, the topography of the patterning device can have variations in sidewall angles. Sidewall angle refers to the angle of the sidewall of the absorber feature relative to the substrate. Thus, for example, referring to FIG. 3 , the sidewalls of the absorber 302 features are shown at 90 degrees relative to the substrate 300 . Variations in the sidewall have a similar effect on the phase as the angle of incidence varies. For example, variations in sidewall angles result in odd phase distribution effects. Thus, in one embodiment, the sidewall angle needs to be controlled within 2 degrees of the normal to avoid the odd phase distribution effect. In one embodiment, the sidewall angle needs to be controlled within 5% of the incident angle range of the illumination. Thus, for example, for 193 nm illumination, the illumination incidence angle may range from approximately -17 degrees to 17 degrees, and thus the sidewall angle should be controlled within 2 degrees, within 1.5 degrees, or within 1 degree. For example, for EUV irradiation, the irradiation incidence angle can range from about 1.5 degrees to 10.5 degrees and thus the sidewall angle should be controlled to within 1 degree, within 0.5 degrees or within 0.3 degrees. However, the sidewall angle can be intentionally varied (instead of or in addition to the angle of incidence) to a specific angle other than 90 degrees to correct for topography-induced phase of the patterning device.

Thus, for a range of incidence angles and/or sidewall angles, the phase distribution is often odd and leads not only to loss of optimum focus but also loss of contrast, loss of depth of focus, pattern asymmetry and/or positioning errors. Also, the phase has a pattern that can generally be described by, for example, Zernike polynomials (eg Zernike term Z3 (ie Nohr index 3) and/or Zernike term Z7 (ie Nohr index 7)). Such a description of the pattern of phases may eg be used to make corrections as discussed further.

Furthermore, in addition to the angle of incidence and/or sidewall angle, the phase also depends significantly on the feature width of the pattern or its features. In particular, the phase range usually scales according to 1/feature width. Typically, the feature width will be one or more critical dimensions (CD) of the pattern or feature, and thus the phase range varies proportionally according to 1/CD.

Thus, as previously mentioned, the topography-induced phase effects of the patterning device are not highly pitch-dependent. Furthermore, by selecting the appropriate CD for the pattern and evaluating the incident angle, an effective correction or optimization can be applied for the entire pattern of the patterning device or a portion of the pattern associated with the selected CD to enable the use of the pattern Improvement or optimization of imaging.

Then, using the measured or otherwise known known values of the topography of the patterning device for which the phase is corrected, the optical wavefront phase can be calculated. This wavefront phase information can then be used to affect changes in parameters of eg the lithographic apparatus or process and/or the patterning device. For example, the calculated optical wavefront phase information can be included in a model (sometimes called a lens model) of the optical system of the lithographic projection system.

One example of a lens model for correcting aberrations is described in US Pat. No. 7,262,831, which is hereby incorporated by reference in its entirety. As mentioned above, the lens model is a mathematical description of the behavior of the optical elements of the projection system.

The overall aberration can be broken down into several different types of aberrations, such as spherical aberration, astigmatism, and so on. The overall aberration is the sum of these different aberrations, each having a specific magnitude given by a coefficient. Aberrations cause deformation of the wavefront, and different types of aberrations represent different functions that the wavefront deformation follows. These functions may take the form of products of polynomials at radial position r and sine or cosine angular functions in mθ, where r and θ are polar coordinates and m is an integer. One such functional expansion is the Zernike expansion, in which each Zernike polynomial represents a different type of aberration and the components of each aberration are given by Zernike coefficients.

Certain types of aberrations, such as focus drift and aberrations with even values of m (or m=0) in the angular function dependent on mθ, can be compensated by means of image parameters that are used to realize the Adjusted so that the projected image is shifted in the vertical (z) direction. Other aberrations, such as coma and aberrations with odd values of m, can be compensated by means of image parameters which are used to achieve an adjustment of the device such that in the horizontal plane (x, y plane) a variation of the image position is produced Lateral offset.

To this end, the lens model also provides indications for setting various lens tuning elements that will give optimized lithographic performance for the particular lens arrangement used and can be used together to optimize the process of exposing many wafers. The imaging performance and overlay of the lithographic equipment are optimized. The expected image parameter offsets (overlap, focus, etc.) are provided to the optimizer, which determines the adjustment signal for which the remaining offsets in the image parameters will be adjusted according to the user-defined lithographic specifications. Minimization (the lithography specification will include, for example, the relative weights assigned to overlay error and focus error and will determine to what extent the maximum allowed value for overlay error (dX) lies above the slit, e.g. Calculated against the maximum allowable value of the focus error (dF) on the slit in the cost function representing optimized image quality). The parameters of the lens model were calibrated offline.

Based on the model including the calculated optical wavefront phase information, one or more parameters used in imaging operations using the lithographic projection system may be calculated. For example, the one or more parameters may include one or more adjustable optical parameters of the lithographic projection system. In an embodiment, the one or more parameters include manipulator settings for an optical element manipulator of the lithographic projection system, such as an actuator for physically deforming the optical element. In an embodiment, said one or more parameters comprise the setting of a device arranged to provide a configurable phase to change the refractive index by localized application of heating/cooling, such as disclosed in US patent application Described in Publication Nos. 2008-0123066 and 2012-0162620, which are hereby incorporated by reference in their entirety. In an embodiment, the calculated optical wavefront phase information is characterized in terms of Zernike information (eg, Zernike polynomials, Zernike coefficients, Nohr exponents, etc.). In an embodiment, wavefront phase information (eg, an expression including, for example, a Zernike expression for an odd-phase distribution) may be used to determine the location of one or more features of the pattern. This positioning may result in, for example, positioning errors, which may be overlay errors. This positioning error or overlay error can be corrected using any known technique, such as changing the position of the substrate relative to the patterned beam.

For example, using measured or otherwise known known values of the topography of the patterning device whose phase is to be corrected, the applicable pattern of the phase (e.g. Zernike polynomials) and the magnitude of the phase (e.g. phase range over diffraction orders magnitude) can be identified. Phase corrections applied based on magnitude and according to the pattern can reduce or remove the undesired phase. In an embodiment, the applicable pattern may comprise a combination of patterns (for example, an even phase distribution pattern selected from, for example, Zernike terms Z4, Z9 and/or Z25 and a pattern selected from, for example, Zernike terms Z3 and/or Z7 combination of odd phase distribution patterns). In pattern combinations, weights can be applied to one or more patterns. For example, in one embodiment, higher weights are applied to odd phase distribution patterns rather than even and odd phase distribution patterns.

In one embodiment, the purpose of this correction is to reduce or minimize the phase range across one or more diffraction orders. That is, referring to Figures 4A-E and Figure 5, the lines shown here are desirably "flattened". In other words, the purpose of this correction is to bring the line shown (or the data associated therewith) close to the horizontal line (or the data generally described by the horizontal line). In an embodiment, the one or more diffraction orders may include diffraction orders having sufficient intensity. Thus, in an embodiment, a diffraction order having sufficient intensity may be a diffraction order exceeding a threshold intensity. Such threshold intensity may be an intensity less than or equal to 30% of maximum intensity, an intensity less than or equal to 25% of maximum intensity, an intensity less than or equal to 20% of maximum intensity, an intensity less than or equal to 15% of maximum intensity, An intensity less than or equal to 10% of the maximum intensity or an intensity less than or equal to 5% of the maximum intensity. Also, weights may be applied to individual diffraction orders by intensity such that, for example, the phase associated with one or more diffraction orders with higher intensity is greater than the phase associated with one or more diffraction orders with lower intensity is corrected more.

This phase correction for normally incident radiation can improve optimal focus. The term "best focus" can be interpreted to mean the plane in which the aerial image with the best contrast is obtained. Also, such phase correction for off-axis illumination (ie, where the radiation is at angles other than or more than orthogonal) and/or sidewall angles can improve optimal focus. Additionally, off-axis illumination and/or sidewall angles have a tendency to result in dual beam imaging. Then, off-axis illumination and/or sidewall angles can be prone to contrast loss, depth of focus loss and possible pattern asymmetry and pattern positioning errors. Correction of phase for off-axis illumination and/or sidewall angles can then improve these other effects.

As is appreciated, if there are one or more "critical" features or "hot spot" patterns that push the imaging of the pattern to or from the boundary of the process window, then The phase for the entire pattern need not be determined. Accordingly, the phase can be determined for such "critical" features, and the correction can thus be focused on those "critical" features. Thus, in an embodiment, where the pattern is a design layout for a device, the optical wavefront phase information is only specified for one or more sub-patterns or features of the patterning device's pattern (ie the design layout).

In an embodiment, the phase may be determined for a number of feature widths, a number of illumination incidence angles, a number of sidewall angles, and/or a number of pitches. Values between them can be interpolated. The phase information can be "painted" onto the pattern and thus yield phase information for a two-dimensional set of patterns. This phase information can be analyzed to discern applicable patterns (eg Zernike polynomials) and phase magnitudes for correction (eg magnitudes across the phase range of diffraction orders).

In an embodiment, one or more properties of the pattern topography can be measured and their values can be used to generate phase information. For example, feature width, pitch, thickness/height, sidewall angle, refractive index, and/or extinction coefficient can be measured. One or more of these properties may be measured using an optical measurement tool, such as that described in US Patent Application Publication No. US2012-044495, which is hereby incorporated by reference in its entirety. The patterning device's metrics can then be used to determine the topography-induced phase of the patterning device, which can then be used to form corrections or designs (eg applied to a lens model of a lithographic apparatus to suit the lithographic process). The devices described in the above patent applications may be referred to as scatterometers or scatterometry tools. Examples of such measurement devices include the Yieldstar product, available from ASML, Eindhoven, The Netherlands. Alternatively, the three-dimensional topography of the reticle can be measured using metrology tools, scanning electron microscopy, or atomic force microscopy. Further details of the scatterometry tool are described below with reference to Figures 17-19.

When designing patterns, designing processes for exposing patterns, and/or designing processes for fabricating devices, computational lithography can be used to simulate aspects of the device fabrication process. In a system for simulating fabrication processes involving lithography and device patterning, major fabrication system components and/or processes may be described by various functional modules, for example, as shown in FIG. 6 . 6, the functional modules may include a design layout module 601, which defines a design pattern (such as a design pattern of a microelectronic device); a patterning device layout module 602, which defines how the pattern of the patterning device is arranged in a polygon based on the design pattern the patterning device model module 603, which models the physical properties of anomalous and continuous tone patterning devices to be used in the simulation process; the optical model module 604, which defines the performance of the optical components of the lithography system; An agent model module 605, which defines the properties of the resist used in a given process; and a process model module 606, which defines the properties of the process (eg, etch) after the resist has been developed. The results of one or more of these simulation modules, such as expected profile, CD, etc., are provided in results module 607 . One, some or all of the above modules may be used in the simulation.

Properties of the illumination and projection optics are captured in the optical modeling module 604, including, but not limited to, numerical aperture and sigma (σ) settings and any particular illumination source parameters such as shape and/or polarization, where σ (or sigma) is the outer radial extent of the illumination source shape. The optical properties of a photoresist layer coated on a substrate, i.e., refractive index, film thickness, propagation and polarization effects, can also be captured as part of the optical model module 604, while the resist model module 605 describes the The effects of chemical processes occurring during resist exposure, post-exposure bake (PEB) and development in order to predict, for example, the profile of resist features formed on a substrate. The patterning device model module 603 captures a representation of how target design features are arranged in the pattern of the patterning device and may include physical properties of details of the patterning device, for example as described in US Pat. No. 7,587,704, which is incorporated by reference in its entirety This article. The goal of the simulation is to accurately predict eg edge positioning and critical dimension (CD), which can then be compared to the target design. The target design is usually defined as the layout of the pre-OPC patterning device and will be provided in a standard data file format such as GDSII or OASIS.

Typically, the link between the optical model and the resist model is the simulated spatial image intensity within the resist layer, which is determined by the projection of radiation onto the substrate, the refraction at the resist interface, and the Multiple reflections in the agent film stack. This radiation intensity distribution (spatial image intensity) is transformed by photon absorption into a potential "resist image", which is further modified by diffusion processes and various loading effects. An efficient simulation method that is fast enough for full-chip applications approximates the realistic 3-dimensional intensity distribution in the resist stack by means of a 2-dimensional spatial (and resist) image.

Thus, the model formulation describes most, if not all, of the known physics and chemistry of the overall process, and each model parameter desirably corresponds to a different physical or chemical effect. The model formulation then sets an upper bound on how well the model can be used to simulate the entire manufacturing process. However, at times, model parameters may be inaccurate due to measurement and reading errors, and other imperfections may exist in the system. With the help of precise calibration of model parameters, extremely accurate simulations can be achieved.

Thus, when performing computational lithography, the topography of the patterning device (sometimes referred to as mask 3D) can be included in the simulations, for example in the patterning device model module 603 and/or the optical model module 604 middle. This can be achieved by converting the topography of the patterning device into a set of cores. Each feature edge of the pattern is convolved with these kernels to produce, for example, a spatial image, see US Patent Application Publication No. 2014/0195993, which is hereby incorporated by reference in its entirety. Accordingly, the accuracy depends on the number of cores. There will be a tradeoff between accuracy (eg number of cores used) and time to run the simulation. Further related techniques for such simulations are described in US Pat. No. 7,003,758, which is hereby incorporated by reference in its entirety.

Accordingly, in one embodiment, the patterning device's topography-induced phase and optionally the patterning device's topography-induced intensity may be used in computational lithography to determine the three-dimensional topography of the patterning device's pattern imaging effect. Thus, referring to FIG. 6B , in one embodiment, the optical wavefront phase and intensity due to the topography of the patterning device may be calculated at 610 . Thus, in an embodiment, optical wavefront phase and intensity information resulting from the three-dimensional topography of features of a pattern of a lithographic patterning device is obtained for multiple pupil positions or diffraction orders. For example, such optical wavefront phase and intensity information resulting from the three-dimensional topography of the features of the patterning device's pattern can be used for multiple angles of incidence, for multiple sidewall angles, for multiple feature widths, Obtained for multiple feature thicknesses, for multiple indices of refraction for pattern features, for multiple extinction coefficients for pattern features, etc.

This optical wavefront phase and intensity information can then be used in 615 for computational lithography calculations instead of or in addition to the core. In an embodiment, optical wavefront phase and intensity information can be represented as core in computational lithography calculations. Then, in 620, the imaging effect of the three-dimensional topography of the patterning device's pattern can be calculated using a computer processor based on the optical wavefront phase and intensity information. In an embodiment, the calculation of the imaging effect is based on the calculation of the diffraction pattern associated with the pattern of the patterning device under consideration. Thus, in one embodiment, calculating the imaging effect involves calculating a multivariate function of a plurality of design variables that are characteristic of the lithographic process, wherein the multivariate function is the calculated optical wavefront phase and intensity function of information. The design variables may include properties of the illumination for the pattern (eg, polarization, illumination intensity distribution, dose, etc.), properties of the projection system (eg, numerical aperture), properties of the pattern (eg, refractive index, physical size, etc.), and the like.

In an embodiment, calculating the imaging effect of the topography of the patterning device includes calculating a simulated image of the pattern of the patterning device. For example, in one embodiment, a "point source" - a delta function (with intensity magnitude A and phase Φ as parameters) can be specified in a simulation at the edge of a feature of the pattern to approximate the topography of the patterning device. For example, the simulation can use the transfer function of illumination as follows:

As mentioned above, the topography-induced phase of the patterning device depends at least on the critical dimension, the sidewall angle and/or the angle of incidence of the radiation. In an embodiment, the delineation or collection range of data for the optical wavefront phase is calculated for a range of angles of incidence of the pattern or features of the pattern and used in computational lithography calculations. In an embodiment, the delineation or collection range of the optical wavefront phase data is additionally or alternatively directed to a critical dimension range of the pattern or a feature of the pattern, to a pitch range of the pattern or a feature of the pattern, Sidewall angle ranges etc. are calculated for a pattern or features of the pattern and used in computational lithography calculations. In one embodiment, the optical wavefront phase is rigorously calculated using a simulator such as Hyperlith software. Interpolation between values can be done where required. A phase map or collection of these data can be precomputed with high precision and can effectively contain full physical information of the topography of the patterning device. The imaging effect of the three-dimensional topography of the pattern of the patterning device can then be calculated using the diffraction pattern of the pattern (which is a pattern-dependent feature) and adding the calculated optical wavefront phase information.

Accordingly, in one embodiment there is provided a method comprising: obtaining calculated optical wavefront phase and intensity information resulting from the three-dimensional topography of a pattern of a photolithographic patterning device; and processing A device is used to calculate an imaging effect of the three-dimensional topography of the pattern of the patterning device based on the calculated optical wavefront phase and intensity information. In one embodiment, obtaining optical wavefront phase and intensity information includes: obtaining three-dimensional topography information of the pattern and calculating optical wavefront phase and intensity information caused by the three-dimensional topography based on the three-dimensional topography information. In an embodiment, calculating the optical wavefront phase and intensity information is based on a diffraction pattern associated with an illumination profile of the lithographic apparatus. In an embodiment, calculating optical wavefront phase and intensity information includes strictly calculating optical wavefront phase and intensity information. In one embodiment, the three-dimensional topography is selected from: the height or thickness of the absorber, the refractive index, the extinction coefficient and/or the side wall angle of the absorber. In an embodiment, the three-dimensional topography includes a multilayer structure including different values of the same property. In an embodiment, the optical wavefront phase information includes optical wavefront phase information for a plurality of critical dimensions of the pattern. In an embodiment, the optical wavefront phase information comprises optical wavefront phase information for a plurality of angles of incidence of the illuminating radiation and/or sidewall angles of the pattern. In an embodiment, the optical wavefront phase information includes optical wavefront phase information for a plurality of pitches of the pattern. In an embodiment, the optical wavefront phase information includes optical wavefront phase information for a plurality of pupil positions or diffraction orders. In an embodiment, calculating the imaging effect of the topography of the patterning device includes calculating a simulated image of the pattern of the patterning device. In an embodiment, the method further includes using the lithographic patterning apparatus to adjust parameters associated with the lithographic process to obtain an enhanced contrast of the imaging of the pattern. In an embodiment, the parameter is a parameter of the topography of the pattern of the patterning device or a parameter of the illumination of the patterning device. In one embodiment, the method further comprises adjusting the refractive index of the patterning device, the extinction coefficient of the patterning device, the side wall angle of the absorber of the patterning device, the height or thickness of the absorber of the patterning device or selected from them Any combination of these to minimize phase variation. In an embodiment, the calculated optical wavefront phase information comprises an odd phase distribution across diffraction orders or a mathematical description thereof.

Therefore, whether using computational lithography supplemented with said optical wavefront phase information, or using conventional computational lithography, it is desirable to correct for the phase introduced by the topography of the patterning device (wavefront phase). Some types of corrections have been described above, some additional types of corrections include adjusting the patterner stack, adjusting the patterner layout, and/or using patterner/illumination adjustments to adjust the patterner illumination (sometimes referred to as optimized for source mask).

Patterning device/illumination (source mask optimization) typically does not take into account the topography of the patterning device or also uses the topography dimension library of the patterning device. That is, the library contains a set of cores derived from the topography of the patterning device. However, as mentioned above, these cores tend to be an approximation, and thus sacrifice accuracy to obtain the desired runtime.

Accordingly, in one embodiment, the patterning device/illumination adjustment calculation involves topography-induced phase (wavefront phase) information of the patterning device. Thus, the influence of the absorber of the patterning device can be described by the phase in the diffraction orders. The topography-induced phase (wavefront phase) of the patterning device then contains all the necessary information.

In an embodiment, as with computational lithography described above, the patterning device/illumination conditioning computation involves topography-induced phase (wavefront phase) information of the patterning device. That is, the mathematical/analog calculations involve phase (wavefront phase) information introduced by the topography of the patterning device. For some basic features, it may be sufficient to use this phase to calculate an optimized patterning device/irradiation pattern combination.

In an embodiment, additionally or alternatively, topography-induced phase (wavefront phase) information of the patterning device is used as a check or control for the patterning device/illumination adjustment calculation. For example, in one embodiment, phase (wavefront phase) information introduced by the topography of the patterning device is used to limit the range of illumination, patterning device and/or other lithographic parameters or to limit the range of illumination, patterning device and/or The bounds of the range of other lithography parameters within which conventional patterning device/illumination conditioning processes perform or are constrained. For example, patterning device topography-induced phase (wavefront phase) information can be obtained for multiple angles of incidence and analyzed to discern acceptable angular ranges within which the patterning device's topography-induced Phase (wavefront phase) is acceptable. Conventional patterning device/illumination conditioning processes can then be performed within this angular range. In an embodiment, a conventional patterning device/irradiation conditioning process may produce one or more proposed combinations of patterning device layouts and illumination patterns. One or more parameters of these one or more combinations may be tested for information on the phase (wavefront phase) introduced by the topography of the patterning device. For example, a plot of the patterning device's topography-induced phase (wavefront phase) versus diffraction order for various angles of incidence can be used in cases where the angle of incidence of the proposed illumination pattern produces a phase magnitude exceeding a threshold Exclude this irradiation mode.

Referring to Figure 7, an exemplary embodiment of a method of patterning device/illumination conditioning is explained. In 701, a lithography problem is defined. The lithography problem represents a specific pattern to be printed onto the substrate. This pattern is used to adjust (eg optimize) the parameters of the lithographic apparatus and to select the correct configuration of the illumination system. Desirably, it represents an aggressive configuration included in the pattern, such as a pattern that groups both dense and isolated features.

In 702, a simulation model is selected that calculates the contour of the pattern. In an embodiment, the simulation model may include an aerial image model. In this case, the distribution of the energy distribution of the incident radiation on the photoresist will be calculated. Computations on spatial images can be done in scalar or vector form in Fourier optics. In particular, the simulation can be carried out by means of commercially available simulators such as Prolith, Solid-C or similar software. Properties of different elements of the lithographic apparatus, such as numerical aperture or specific patterns, can be employed as input parameters for the simulation. Different models can be used, such as Lumped Parameter Model or Variable Threshold Resist model.

In this particular embodiment, relevant parameters for running an aerial image simulation may include the distance to the plane in which the plane of best focus lies, a measure of the degree of coherence of the spatial portion of the illumination system, the illumination polarization, the A description of the numerical aperture of the optical system, the aberrations of the optical system, and the spatial transfer function representing the patterning device. In an embodiment, as described above, the relevant parameter may comprise topography-induced phase (wavefront phase) information of the patterning device.

It should be understood that the use of the simulation model selected in 702 is not limited to the calculation of resist profiles, for example. Simulation models can be performed to extract additional/complementary responses such as process latitude, dense/isolated feature bias, side lobe printing, sensitivity to patterning device errors, and the like.

After defining the model and its parameters, including initial conditions for the pattern and illumination pattern, the method then proceeds to 703 where the simulation model is run to calculate the response. In an embodiment, with respect to computational lithography, the simulation model may be calculated based on topography-induced phase (wavefront phase) information of the patterning device as described above. Thus, in one embodiment, the simulation model embodies a multivariate function of a plurality of design variables that are characteristics of the photolithography process, the design variables including the illumination characteristics of the pattern and the characteristics of the pattern, wherein the multiple The variable function is a function of the calculated optical wavefront phase information.

In 704, one or more irradiation conditions of the irradiation pattern (e.g., changing the type of intensity distribution, changing a parameter of the intensity distribution (such as σ), changing the dose, etc.) and/or the layout or shape of the pattern of the patterning device One or more aspects of the morphology (eg, applying a bias, adding optical proximity effect correction, changing absorber thickness, changing refractive index or extinction coefficient, etc.) are adjusted based on analysis of the response.

The calculated response in this embodiment can be evaluated against one or more photolithography metrics to determine, for example, whether there is sufficient contrast to successfully print the desired pattern features in the resist on the substrate. For example, aerial images can be analyzed by focus range to provide estimates of exposure latitude and depth of focus and the procedure can be iteratively performed to arrive at optimal optical conditions. In fact, the quality of the spatial image can be determined by using contrast or spatial image log slope (ILS) measure, which can be the normalized image log slope measure (NILS), the normalized image log slope The slope measure may eg be normalized with respect to the feature size. This value corresponds to the slope of the image intensity (or spatial image). In one embodiment, lithography metrics may include critical dimension uniformity, exposure latitude, process window, size of process window, mask error enhancement factor (MEEF), normalized image log slope (NILS), edge localization error and/or pattern fidelity metrics.

As mentioned above, in one embodiment, phase (wavefront phase) information introduced by the topography of the patterning device may be used to evaluate or constrain the computation of this response. For example, in one embodiment, phase (wavefront phase) information introduced by the topography of the patterning device is used to limit the range of illumination, patterning device and/or other lithographic parameters or to limit the range of illumination, patterning device and/or The bounds of the range of other lithography parameters within which conventional patterning device/illumination conditioning processes perform or are constrained to generate a response. For example, topography-introduced phase (wavefront phase) information of the patterning device can be obtained for multiple angles of incidence and analyzed to discern acceptable angular ranges within which the topography-introduced phase of the patterning device Phase (wavefront phase) is acceptable. Conventional patterning device/illumination conditioning processes can then be performed within this angular range. In an embodiment, a conventional patterning device/irradiation conditioning process may produce one or more proposed combinations of the patterning device's pattern configuration and illumination mode in response. One or more parameters of these one or more combinations may be tested for information on the phase (wavefront phase) introduced by the topography of the patterning device. For example, a plot of the patterning device's topography-induced phase (wavefront phase) versus diffraction order for various angles of incidence can be used in cases where the angle of incidence of the proposed illumination pattern produces a phase magnitude exceeding a threshold Exclude this irradiation mode.

In 705, the simulation/computation, determination of the response and evaluation of the response may be repeated until certain termination conditions are met. For example, the adjustment may continue until a value is minimized or maximized. For example, lithography metrics, such as critical dimension, exposure latitude, contrast, etc., may be evaluated for satisfying design criteria (eg, critical dimension less than a certain first value and/or greater than a certain second value). This adjustment may continue if the lithography metrics do not meet the design criteria. In an embodiment, for the adjustment, topography-induced phase (wavefront phase) information of the new patterning device may be used or obtained (eg, calculated).

Furthermore, in addition to patterning device/illumination adjustments, one or more other parameters of the lithographic apparatus or process may also be adjusted. For example, one or more parameters of a projection system of a lithographic apparatus may be adjusted, such as numerical aperture, aberration parameters (eg, parameters associated with means that may adjust aberrations in the beam path), etc.

Accordingly, in an embodiment there is provided a method comprising: for irradiation with radiation of a pattern of a lithographic patterning device, obtaining calculated optical wavefront phase information resulting from the three-dimensional topography of the pattern; and adjusting parameters of the illumination and/or adjusting parameters of the pattern based on the optical wavefront phase information and using a computer processor. In an embodiment, the method further includes: for the adjusted illumination and/or pattern parameters, obtaining the calculated optical wavefront phase information caused by the three-dimensional topography of the pattern and adjusting the illumination parameters and/or adjusting the pattern parameter, where the steps of obtaining and adjusting are repeated until a certain termination condition is met. In an embodiment, the step of adjusting comprises calculating a lithographic measure based on the optical wavefront phase information and adjusting parameters of the illumination and/or pattern based on the lithographic measure. In one embodiment, the lithography metrics include one or more selected from the group consisting of: critical dimension uniformity, exposure latitude, process window, size of process window, mask error enhancement factor (MEEF), normalized image Logarithmic slope (NILS), edge localization error or pattern fidelity measure. In an embodiment, the step of obtaining includes obtaining the calculated optical wavefront phase information for a plurality of different angles of incidence of the illuminating radiation; and wherein the step of adjusting includes defining the incident wavefront phase information based on the calculated optical wavefront phase information. An acceptable angular range of radiation is irradiated and parameters of the illumination and/or pattern are adjusted within this defined angular range. In an embodiment, the adjusting step includes performing an optimization of the illumination/patterning device. In one embodiment, the step of adjusting includes calculating a multivariate function of a plurality of design variables that are properties of the lithographic process, the design variables including properties of the illumination to the pattern and properties of the pattern, wherein the The multivariate function is a function of the calculated optical wavefront phase information.

In an embodiment, there is provided a method for improving a photolithographic process for imaging at least a portion of a pattern of a photolithographic patterning device onto a substrate, the method comprising: obtaining a calculated three-dimensional Optical wavefront phase information due to topography; using a computer processor to compute a multivariate function of parameters that are characteristic of the lithographic process, including characteristics of the illumination to the pattern and characteristics of the pattern , wherein the multivariate function is a function of the calculated optical wavefront phase information; and adjusting a characteristic of the lithography process by adjusting one or more of the parameters until a predetermined termination condition is met.

In one embodiment, the step of adjusting further comprises calculating another multivariate function of a plurality of design variables that are characteristics of the lithography process, wherein the other multivariate function is not the calculated optical wavefront phase information The function. In one embodiment, the multivariate function is used for critical regions of the pattern and the other multivariate function is used for non-critical regions. In one embodiment, the adjusting step increases the contrast of the imaging of the pattern. In an embodiment, the calculated optical wavefront phase information comprises an odd phase distribution across diffraction orders or a mathematical description thereof. In one embodiment, the obtaining step includes obtaining three-dimensional topography information of the pattern and calculating optical wavefront phase information caused by the three-dimensional topography based on the three-dimensional topography information. In an embodiment, the pattern is the design layout of the device and optical wavefront phase information is only specified for sub-patterns of the pattern. In an embodiment, the method includes adjusting an illumination parameter, wherein adjusting the illumination parameter includes adjusting an illumination intensity distribution. In an embodiment, the method includes adjusting pattern parameters, wherein adjusting the pattern parameters includes applying optical proximity correction features and/or resolution enhancement techniques to the pattern. In an embodiment, the optical wavefront phase information comprises optical wavefront phase information for a plurality of angles of incidence of radiation and/or sidewall angles of the pattern. In one embodiment, said obtaining step includes strictly calculating optical wavefront phase information.

Patterning device stack tuning (eg, optimization) is primarily achieved by looking at manufacturability aspects (eg, etch). If imaging using the patterning device is part of the conditioning step, it is done using one or more derived imaging figures of merit (eg exposure latitude) of the measure. These derived imaging figures of merit are feature and illumination setting dependent. When using a derived image figure of merit (such as exposure latitude) for an adjustment, it may not be clear if the derived adjusted stack is substantially better across all imaging-related subjects because the adjustment The steps depend on features, illumination settings, and the like.

Accordingly, instead of or in addition to evaluating derived imaging metrics such as exposure latitude, the topography-induced phase of the patterning device (wavefront phase) is evaluated. By evaluating the phase (wavefront phase) introduced by the topography of the patterning device for stack properties (e.g., refractive index, extinction coefficient, absorber or other height/thickness, sidewall angle, etc.) of one or more patterning devices Dependence on , it is possible to discern modified patterning device stacks that reduce or minimize the magnitude of the mask 3D-induced phase. Mask stacks derived in this manner may be fundamentally better in multiple imaging properties for all features and/or illumination settings.

Referring to FIG. 8A , there is shown a graph of simulated intensities (in terms of diffraction efficiency) of diffraction orders exposed with normal incidence 193 nm illumination for a binary mask and an optimized phase shift mask with an approximately 6% MoSi absorber. . Referring to FIG. 8B , there is shown a graph of simulated phases of diffraction orders exposed with normal incidence 193 nm illumination for a binary mask and a phase shift mask with an approximately 6% MoSi absorber. The graph shows the results for the binary mask 800 and the phase shift mask.

The graphs in Figures 8A and 8B show simulation results of how the measured diffraction efficiency and wavefront phase change as a function of diffraction order, respectively. This simulation models the projection of the mask pattern when exposed to the 193 nm radiation and can be performed, for example, using Hyperlith software (available from Panoramic Technology, Inc). The phase is in radians and the diffraction orders are integers, with 0 corresponding to the 0th diffraction order. The simulation was performed for binary mask 800 and phase shift mask 802 .

Referring to Figure 8A, it can be seen that the two different masks 800, 802 provide quite comparable diffraction efficiency performance over the range of diffraction orders. Additionally, the diffraction efficiency of the phase shift mask 802 is slightly higher for the first and second diffraction orders. Thus, a thinner absorber 802 can provide better performance than the binary mask 800 .

Here, referring to Figure 8B, it can be seen that the binary mask 800 and the phase shift mask 802 provide quite different wavefront phase properties over the range of diffraction orders. In particular, for phase shift mask 802, the phase range across one or more of the diffraction orders is generally reduced compared to binary mask 800. That is, for the phase shift mask 802, the phase range across diffraction orders is reduced or minimized compared to the binary mask 800. This can be seen in FIG. 8B as the line representing the phase shift mask 802 being generally "flattened" compared to the line representing the binary mask 800 . In other words, the lines representing the phase shift mask 802 are generally closer to the horizontal than the binary mask 800 .

Referring to FIG. 9A , it shows the phase (wavefront phase) (in radians) and diffraction order (wherein the 0th diffraction order Diagram corresponding to 7.5) relationship. The graph shows the results of binary masks for three different absorber thicknesses (nominal, 6nm less than nominal (-6nm) and 6nm greater than nominal). The graph shows that a thinner absorber (-6 nm) yields slightly better performance as its lines are more flattened than the other cases.

Here, referring to Figure 9B, more specific details of the effect of absorber thickness can be seen. Figure 9B shows the graph of the simulated patterning device's topography-introduced phase (wavefront phase) in radians versus the change in absorber thickness from the nominal value in nanometers for the binary mask of Figure 9A Relationship diagram. In this graph, three different figures of merit are applied to the phase versus diffraction order graph. The first figure of merit is the total phase range (see "Total" in the illustration). The second figure of merit is the peak range (see "Peaks" in the inset). Also, the third figure of merit is the range of high order (see "High order" in the illustration). Referring to Figure 9B, it can be seen that the peak range ("peak") of the phase is substantially constant. However, for higher orders ("higher orders"), the phase range increases with the thickness of the absorber and thus the higher orders mainly drive the variation of the total phase range ("total"). One or more of these figures of merit may then be used to drive the configuration of the stack of patterning devices. For example, a higher order figure of merit recommends thinner absorbers to reduce the phase range. Correspondingly, for example a minimum value (or a value in 5%, 10%, 15%, 20%, 25% or 30% of this minimum value) of the figure of merit of a higher order can achieve a suitable thickness of the binary mask . However, since the phase peak range is a substantially constant non-zero number over the thicknesses shown, there are no alternatives to reducing the higher order phase range or using very large thicknesses (which may not be manufacturable or usable in practice). ), the further benefit of reducing the phase range is not much, if any. Accordingly, changes in the refractive index and/or extinction coefficient may be required.

Referring to FIG. 10A , the simulated topography-induced phase of the patterning device is shown for the case where a phase-shift mask with a 6% MoSi absorber (i.e., the patterning device has a different refractive index) is exposed to normal incidence 193 nm radiation. A graph of (wavefront phase) (in radians) versus diffraction order (where 0th diffraction order corresponds to 7.5). The graph shows that for three different absorber thicknesses (the nominal value (which is an optimized number and corresponds to the phase shift mask 802 in FIGS. 8A and 8B ), 6 nm less (-6 nm) than the nominal value and Larger than 6nm) results. The graph shows that the nominal thickness yields significantly better performance as its line is flatter than the other cases.

Here, referring to FIG. 10B , more specific details of the effect of absorber thickness can be seen. Figure 10B shows the topography-induced phase (wavefront phase) (in radians) of the simulated patterning device for the phase shift mask of Figure 10A with a 6% MoSi absorber versus absorber thickness from nominal A graph of the relationship between the change (in nanometers). As in the graph of Figure 9B, three different figures of merit ("total", "peak" and "higher order") are identified as applied to the phase versus diffraction order graph.

Referring to Figure 10B, it can be seen that the phase peak range ("Peak"), the phase range for higher orders ("Higher Order") and the total phase range ("Total") are all varied. Thus, one or more of these figures of merit may be used to drive the configuration of the patterning device stack in order to tune the stack. For example, the peak figure of merit can drive the configuration of the stack to reduce the phase range. Accordingly, for example, a minimum value of the peak quality factor (or a value within 5%, 10%, 15%, 20%, 25% or 30% of the minimum value) can achieve a suitable thickness of the mask (such as in nominal thickness in Figure 10B). Alternatively, more than one figure of merit may be used to drive the configuration of the stack of patterning devices. The adjustment process may then involve a co-optimization problem (perhaps giving appropriate weights to certain figures of merit and/or not exceeding thresholds applied to these figures of merit) involving more than one figure of merit. Accordingly, for example, a co-optimized minimum value (or a value within 5%, 10%, 15%, 20%, 25% or 30% of the minimum value) may achieve a suitable thickness of the mask.

It should be understood that the same analysis can be applied to patterning device absorbers having different refractive indices, different extinction coefficients, etc. to tune (eg optimize) the patterning device stack. Therefore, in addition to the above-mentioned optimization of the thickness for the special combination of the refractive index, extinction coefficient, etc., it is also possible to perform similar optimization for different refractive indices for the special combination of thickness, extinction coefficient, etc., for the thickness, refractive index, etc. Special combinations are similarly optimized for different extinction coefficients, etc. And thus, these results can be used to co-optimize functions to arrive at a tuned (eg optimized) stack. Although the physical parameters of the topography of the patterning device have been described, the parameters forming the topography of the patterning device (eg etching) may be similarly considered.

Referring to FIG. 11 , it is shown that the simulated best focus difference (in nanometers) and pitch (in is a graph of the relationship between nanometers). As can be seen in Figure 11, phase shift mask 802 provides an overall lower sweet spot difference than phase shift mask 800 and compensates for the apparent patterning device topography at a pitch of about 80-110 nm Introduced best focus position difference.

Referring to Figures 12A and 12B, a binary mask with a thin absorber and a phase shift mask with an approximately 6% MoSi absorber (corresponding to phase shift mask 802 in Figures 8A and 8B and with Figure 10A The performance comparison of the nominal value thickness in ). Here, the comparison is also shown for various angles of incidence of the illumination. Thus, FIG. 12A shows that for a binary mask a σ(sigma) of -0.9 corresponds to an angle of incidence of -16.5 degrees, a σ of 0 corresponds to an angle of incidence of 0 degrees, and a value of 0.9 corresponds to an angle of incidence of 16.5 degrees. A graph of the relationship between the simulated patterning device's topography-introduced phase (wavefront phase) (in radians) and the diffraction order under 193nm radiation exposure of σ. The graph shows that for each illumination angle, the phase range Δ is quite distinct, including the total phase range, the peak phase range and to some extent the higher order phase range. Therefore, this binary mask gives a contrast loss and has a significant best focus difference.

FIG. 12B shows that for a phase shift mask with a MoSi absorber of about 6% (corresponding to phase shift mask 802 in FIGS. 8A and 8B and having a nominal thickness in FIG. 10A ) is corresponding to a -16.5 degree incident angle σ(sigma) of -0.9, σ of 0 corresponding to an incident angle of 0 degrees, and σ of 0.9 corresponding to an incident angle of 16.5 degrees of 193 nm radiation exposure of the simulated patterning device topography introduced by A plot of phase (wavefront phase) in radians versus diffraction orders (in integers). The graph shows that for each illumination angle, the phase range Δ is quite narrow in diffraction orders and thus the mask gives low contrast loss, low best focus difference, low positioning error and relatively low pattern asymmetry.

Referring to Figures 13A and 13B, a binary mask with a thin absorber and a phase shift mask with an approximately 6% MoSi absorber (corresponding to phase shift mask 802 in Figures 8A and 8B and with Figure 10A Comparison of optimal focus and contrast for nominal thickness in . Here, the comparison is shown also for dense features 1300 and semi-isolated features 1302 of the pattern. Thus, Figure 13A shows a graph of measured dose sensitivity (in nm/mJ/ ^cm2 ) versus best focus (in nm) for a binary mask exposed to 193 nm radiation. The dose sensitivity scale on the left hand side is for dense features 1300 and the dose sensitivity scale on the right hand side is for semi-isolated features 1302 . The graph shows, for example, that the minimum value of dose sensitivity (marked by arrow 1304) for dense features 1300 is at a significantly different optimum than the minimum value of dose sensitivity (marked by arrow 1306) for semi-isolated features 1302. focus position.

Figure 13B shows the measured dose sensitivity (in units It is a graph of the relationship between nm/mJ/cm ² ) and the best focus position (unit: nm). The dose sensitivity scale on the left hand side is for dense features 1300 and the dose sensitivity scale on the right hand side is for semi-isolated features 1302 . 13A, the graph shows, for example, that the minimum of dose sensitivity (marked by arrow 1304) for dense features 1300 is at a minimum close to the minimum of dose sensitivity (marked by arrow 1306) for semi-isolated features 1302 best focus position. Also, the dose sensitivity across the best focus range for both dense and semi-isolated features is generally lower for phase-shift masks than for binary masks. In fact, for semi-isolated features, the dose sensitivity decreases significantly overall as indicated by the horizontal arrows. Figure 13B also shows that the sweet spot range (approximately -190nm to -50nm) is significantly reduced for dense features and semi-isolated features compared to that in Figure 13A (approximately -190nm to 0nm). Thus, a tuned phase-shift mask (corresponding to phase-shift mask 802 in FIGS. 8A and 8B and having a nominal value thickness in FIG. 10A ) with a MoSi absorber of about 6% can provide optimal focus and contrast Provide clear benefits.

Referring to Figures 14A and 14B, the topography-induced phase (wavefront phase) (in radians) versus diffraction order for a simulated patterning device for an EUV mask with a 22nm line/space pattern pass pitch is shown. Relationship diagram. Figure 14A shows the results for features in a first direction (vertical features), and Figure 14B shows the results for features in a second direction substantially orthogonal to the first direction (horizontal features). In an EUV arrangement, where the mask is reflective, the chief ray is incident on the patterning device at non-zero and non-90 degree angles to the patterning device. In one embodiment, the chief ray angle is about 6 degrees. Correspondingly, referring to Fig. 14B, due to the angle of incidence of the chief ray, the phase distribution is generally always odd for horizontal features (similar to the non-normal incidence angles described above with respect to Fig. 5) (and thus one can use e.g. pattern to correct). Also, referring to Figure 14A, the phase distribution is generally even for vertical features (and thus can be corrected using patterns such as Zernike terms Z9 or Z16).

Referring to FIGS. 15A and 15B , the topography-induced phase (wavelength) of the simulated patterning device is shown for an EUV mask with a 22 nm line/space pattern passing pitch and for various angles relative to the inclined chief ray. A graph of the relationship between the front phase) (in radians) and the diffraction order. Figure 15A shows the results for features in a first direction (vertical features), and Figure 15B shows the results for features in a second direction substantially orthogonal to the first direction (horizontal features). As seen in Figure 15A for the angular range of -4.3 degrees to 4.5 degrees relative to the chief ray angle (6 degrees in this case), the phase distribution is substantially even for vertical features and thus one can use e.g. Zernike Item Z9 or Z16 pattern to correct. Also, referring to FIG. 15B , for the angular range of -4.3 degrees to 4.5 degrees relative to the chief ray angle (in this case, 6 degrees), the phase distribution is odd for horizontal features and thus one can use, for example, the Zernike term Z2 or Z7 pattern to correct.

Thus, in one embodiment, while the absorber properties may be modified to help correct the patterner's topography-induced phase (wavefront phase) of the EUV mask, for correcting the patterner's topography-induced phase Another way of (wavefront phase) is to provide off-axis illumination that resolves the odd phase distribution associated with the horizon and mitigates fading. For example, bipolar illumination (with poles in place) can provide illumination for both horizontal and vertical lines, but fits better with horizontal lines. 16 shows the simulated modulation transfer function (MTF) versus coherence for various line and space patterns for a patterning device of an EUV lithographic apparatus with a numerical aperture of 0.33 and using bipolar illumination with a ring width of 0.2. relation. Line 1600 shows the results for the 16nm line and spacer pattern, line 1602 shows the result for the 13nm line and spacer pattern, line 1604 shows the result for the 12nm line and spacer pattern, and line 1606 shows the result for the 11nm line and spacer pattern. The MTF is a measure of the amount of first order diffracted radiation captured by the projection system. The values of the coherence on the graph of Figure 16 give the center of the pole position (σ) for the various line and space patterns with respect to the dipole illumination of the inclined chief ray. Thus, it can be seen from Fig. 16 that for 16nm line-and-space patterns illuminated by EUV radiation and larger, relatively low angles (coherence > 0.3) with respect to the oblique chief ray can be chosen to preserve maximum modulation. Simultaneously controlling the phase of the topography introduction of the patterning device. In contrast, for (radiation of) 193nm, a 40nm line and space pattern may require σ = 0.9 (17 degree angle of incidence).

Also, for EUV irradiation, for example, the effect of the topography-induced phase (wavefront phase) of the patterning device can be different not only for each orientation (e.g. vertical or horizontal features), but also for each pitch. different. For different feature orientations and different pitches, there are differences in optimal focus positions, Bossung curve slopes, differences in contrast across pitches, and/or differences in depth of focus.

In one embodiment, the techniques used to estimate the phase (e.g., using a figure of merit, co-optimization, etc.) can be applied herein to other embodiments where, instead of or in addition to the patterning device stack properties, the altered parameters are the incident angle of the illuminating radiation, the side wall angle, the critical dimension, etc.

Accordingly, in one embodiment, a method is provided, the method comprising: obtaining optical wavefront phase information caused by the three-dimensional topography of a pattern of a photolithographic patterning device; based on the optical wavefront phase information and using computer processing to adjust the physical parameters of the pattern. In an embodiment, the pattern is the design layout of the device and optical wavefront phase information is only specified for sub-patterns of the pattern. In one embodiment, the method further includes: for the adjusted physical parameters of the pattern, obtaining the optical wavefront phase information caused by the three-dimensional topography of the pattern and adjusting the parameters in the physical parameters of the pattern, wherein the obtaining step The and adjustment steps are repeated until certain termination conditions are met. In one embodiment, the adjusting step increases the contrast of the imaging of the pattern. In an embodiment, the calculated optical wavefront phase information comprises an odd phase distribution across diffraction orders or a mathematical description thereof. In an embodiment, the adjusting step includes determining a minimum value of the phase caused by the three-dimensional topography of the pattern of the photolithographic patterning device. In one embodiment, the physical parameters include one or more selected from the group consisting of: refractive index, extinction coefficient, sidewall angle, thickness, feature width, pitch, and/or stack parameters (e.g., order/composition/ wait). In an embodiment, adjusting the physical parameter includes selecting a patterned absorber from a library of absorbers. In one embodiment, obtaining the optical wavefront phase information includes strictly calculating the optical wavefront phase information.

Thus, in one embodiment, the topography-induced phase (wavefront phase) of the patterning device is used to tune (eg optimize) the stack of patterning devices. In particular, wavefront phase effects can be mitigated by absorber tuning (eg optimization). In one embodiment, as described above, an opaque binary mask may not be suitable, while a transmissive phase-shift mask with an optimized absorber thickness can improve the wavefront phase and lithographic performance on the substrate. aspect gives the best performance.

Also, for EUV patterning devices, contrast loss due to odd phase distribution effects can be best mitigated by illumination pattern adjustment (eg optimization).

In an embodiment, the topography-induced phase (wavefront phase) of the patterning device can be used to adjust (eg optimize) the patterning device to patterning device variance. That is, information on the topography-induced phase (wavefront phase) of the patterning device for each individual patterning device can be compared or monitored to identify differences between the patterning devices, for example to apply corrections to lithographic parameters of the process (e.g. corrections to one or more patterning devices, changes to illumination patterns, application of phase compensation in a lithographic apparatus, etc.) to make them similar in performance (this may involve making the performance "worse ” or “better”). Thus, in one embodiment, monitoring of phase differences between different patterning devices (eg, patterning devices of one or more similar critical patterns, features or structures) and adjustment of the lithographic process to compensate for the phase difference is provided. Determined differences (eg, corrections to one or more patterning devices, changes to illumination patterns, application of phase compensation in a lithographic apparatus, etc.). This approach can advantageously be applied to nominally identical patterning devices. That is, where a manufacturer has multiple "copies" of a particular patterning device, changes in the production or handling of the patterning device will likely result in different phase performance. For example, one copy may be a substitute for another copy, or in the case of particularly high-volume production, there may be many copies being used in parallel on several different lithography systems. Thus, it may be useful to have slightly different patterning devices perform more similar adjustments to parameters though.

In an embodiment, the topography-induced phase (wavefront phase) of the patterning device can be used to adjust (eg optimize) the variation across the patterning device. That is, the topography-induced phase of the patterning device (wavefront phase) for different patterns or regions on the patterning device can be compared to identify differences between the regions and apply corrections, for example, to photolithographic processes. parameters (such as corrections to one or more regions of the patterning device, changes to illumination patterns, application of phase compensation in lithographic apparatus, etc.) to make them similar in performance (this may involve making the performance "variable") worse” or “better”). Thus, in one embodiment, monitoring of phase differences across patterning devices (e.g., patterning devices of one or more similar critical patterns, features, or structures) is provided and the lithography process is adjusted to compensate for the determined differences (eg corrections to one or more patterning devices, changes to illumination patterns, application of phase compensation in lithographic apparatus, etc.). The compensation can be performed dynamically, for example during a scanning operation of the lithographic apparatus. This causes different regions of the patterning device to experience different phase compensations as the patterning device is relatively scanned and imaged onto the substrate. By way of example, a pattern that is sparse on one side and dense on the other, or a pattern in which the critical dimension varies across the mask pattern, may represent a variation of the phase effect as the scan progresses. This type of change in scan position can be compensated for in operation by adjusting imaging parameters as described herein.

Thus, one or more of these techniques can provide a significant improvement in the precision with which a lithographic apparatus can project one or more patterns onto a substrate.

Some of the techniques here for correcting the wavefront phase, for example for mitigating focus differences by varying absorber thickness, can reduce the contrast of aerial images formed using the patterning device. In some areas of application this may not be of great concern. For example, if a lithographic apparatus is being used to image patterns that will form logic circuits, contrast may be considered less important than poor focus. The benefits provided by the improvement in focus difference (eg better critical density uniformity) may be considered more important than the reduced contrast. A suitable optimization function (eg weighting with lithographic measurements) can be used to arrive at a balance (eg optimal value). For example, in an embodiment, the phase shift provided by the patterning device and the contrast improvement it provides can be taken into account, and the topography-induced phase of the patterning device can be used when correcting, for example, the topography-induced phase of the patterning device. be considered. A compromise can be found that provides the necessary degree of contrast while providing reduced topography-induced phase of the patterning device.

In the above embodiments, the absorbent material has generally been described as a single material. However, the absorbent material may be more than one material. The material may eg be provided in layers, and may eg be provided in a stack of alternating layers. In order to change the refractive index or extinction coefficient, different materials with the desired refractive index/extinction coefficient can be used, and dopants can be added to the absorber in relative proportions of the constituent elements of the absorber material (such as the ratio of molybdenum to silicide). in the material.

Returning to the inspection apparatus described above with reference to FIG. 2 , FIG. 17 shows an embodiment of the scatterometer SM1 . The scatterometer includes a radiation projection device 1702 , which may be a broadband (white light) projection device, which projects radiation onto a substrate under inspection 1706 . It should be understood that in a typical application, the substrate is a printed wafer with inspection targets thereon. However, in the context of the present invention, the substrate being inspected is the substrate of the patterning device. The reflected radiation passes to a spectrometer detector 1704, which measures the spectrum 1710 of the specularly reflected radiation (ie, a measure of intensity as a function of wavelength). From this data, the structure or profile resulting in the detected spectrum can be reconstructed by the processing unit PU, for example, by rigorous coupled wave analysis and nonlinear regression or comparison with a simulated spectral library as shown at the bottom of FIG. 17 . Usually, for the reconstruction, the general form of the structure is known, and by assuming some parameters from knowledge of the fabrication process of the structure, only a few parameters of the structure are left to be determined from scatterometry data. This scatterometer can be configured as a normal incidence scatterometer or an oblique incidence scatterometer.

Another embodiment of scatterometer SM2 is shown in FIG. 18 . In this arrangement, radiation emitted by a radiation source 1802 is focused using a lens system 1812 and passed through an interference filter 1813 and a polarizer 1817, reflected by a partially reflective surface 1816 and transmitted through a channel having a high numerical aperture (NA) (ideally at least 0.9 or A microscope objective 1815 of at least 0.95) is focused onto the substrate. Immersion scatterometers can even have lenses with numerical apertures exceeding 1. The reflected radiation is then transmitted through the partially reflective surface 1816 into a detector 1818 for detection of the scatter spectrum. The detector may be located on the back-projected pupil plane 1811 at the focal length of the lens 1815, however, the pupil plane may instead be re-imaged on the detector 1818 by auxiliary optics (not shown). The pupil plane is the plane in which the radial position of the radiation defines the angle of incidence and the angular position defines the azimuthal angle of the radiation. The detector is ideally a two-dimensional detector so that a two-dimensional angular scatter spectrum of the substrate target can be measured (ie, the intensity is measured as a function of scattering angle). Detector 1818 may be, for example, an array of charge-coupled devices (CCD) or complementary metal-oxide-semiconductor (CMOS) sensors, and may have an integration time of, for example, 40 milliseconds per frame.

Reference beams are often used, for example, to measure the intensity of incident radiation. To this end, when a radiation beam is incident on partially reflective surface 1816 , a portion of the radiation beam is transmitted through the surface as a reference beam travels towards reference mirror 1814 . The reference beam is then projected onto a different portion of the same detector 1818 .

One or more interference filters 1813 may be used to select wavelengths of interest in a range such as 405-790nm or even lower (eg 200-300nm). Interference filters may be tunable rather than comprising a set of different filters. Gratings may be used instead of or in addition to one or more interference filters.

Detector 1818 may measure the intensity of scattered radiation at a single wavelength (or narrow wavelength range), the intensity being discrete at multiple wavelengths, or the intensity being concentrated over a wavelength range. Furthermore, the detector may independently measure the intensity of transverse magnetic (TM) and transverse electric (TE) polarized radiation and/or the phase difference between transverse magnetic and transverse electric (TE) polarized radiation.

A broadband radiation source 1802 can be employed that gives a large etendue (ie, has a broad range of radiation frequencies or wavelengths and thus a large range of colors), thereby allowing mixing of multiple wavelengths. The multiple wavelengths in the broadband desirably each have a bandwidth of δλ and a spacing of at least 2δλ (ie twice the wavelength bandwidth). The multiple radiation "sources" may be different parts of an extended radiation source that has been divided using, for example, fiber optic bundles. In this way, angle-resolved scatter spectra can be measured at multiple wavelengths in parallel. A three-dimensional spectrum (wavelength and two different angles) can be measured which contains more information than a two-dimensional spectrum. This allows more information to be measured which increases the robustness of the measurement process. This is described in more detail in US Patent Application Publication No. US2006-0066855, which is incorporated herein by reference in its entirety.

By comparing one or more properties of the beam before and after the beam has been redirected by the target, one or more properties of the substrate may be determined. This can be done, for example, by comparing the redirected beam with a theoretical redirected beam calculated using a model of the substrate, and by comparing the optimal beam given by the measured and calculated redirected beam. This is achieved by searching for the best-fitting model. Typically, a parameterized general model is used and parameters of the model such as width, height and sidewall angle of the pattern are varied until the best fit is obtained.

Two main types of scatterometers are used. A spectroscopic scatterometer directs a broadband radiation beam onto a substrate and measures the spectrum (intensity as a function of wavelength) of the radiation scattered into a specific narrow angular range. Angle-resolved scatterometers use a monochromatic radiation beam and measure the intensity (or intensity ratio and phase difference in the case of an ellipsometer configuration) of the scattered radiation as a function of angle. Alternatively, measurement signals of different wavelengths can be measured individually and in combination in the analysis phase. Polarized radiation can be used to generate more than one spectrum from the same substrate.

In order to determine one or more parameters of the substrate, it is common to compare the theoretical spectrum produced by the substrate model with the measurements produced by the redirected beam as a function of wavelength (spectroscopic scatterometer) or angle (angle-resolved scatterometer). Find the best match between spectra. There are many methods that can be combined to find this best match. For example, a first method is an iterative search method, where a first set of model parameters is used to calculate a first spectrum, which is compared with the measured spectrum. A second set of model parameters is then selected, a second spectrum is calculated and a comparison of the second spectrum with the measured spectrum is made. These steps are repeated with the aim of finding said set of parameters that gives the best matching spectrum. Typically, the information derived from the comparison is used to steer the selection of subsequent group parameters. This process is known as an iterative search technique. The model with the set of parameters that gives the best match is considered the best description of the measured substrate.

A second approach is to create a library of spectra, each spectrum corresponding to a particular set of model parameters. Typically, sets of model parameters are chosen to cover all or nearly all possible variations in substrate properties. The measured spectra are compared with the spectra in the library. Similar to the iterative search method, the model with the set of parameters corresponding to the spectrum giving the best match is considered to be the best description of the measured substrate. Interpolation techniques can be used to more precisely determine the optimal set of parameters in this library search technique.

In any method, sufficient data points (wavelength and/or angle) in the calculated spectra should be used to enable an accurate match, typically 80 to 800 data points or more for each spectrum between data points. Using an iterative approach, each iteration for each parameter value would involve calculations at 80 or more data points. This is multiplied by the number of iterations required to obtain the correct contour parameters. Thus many calculations may be required. In practice, this leads to a trade-off between accuracy and processing speed. In library approaches, there is a similar trade-off between accuracy and the time required to build the library.

In any of the scatterometers discussed above, the target on the substrate may be a grating that is printed such that after development the stripes consist of solid resist lines. The stripes may alternatively be etched into the substrate. The target pattern is chosen to be sensitive to parameters of interest such as focus, dose, overlap, chromatic aberration, etc. in the lithographic projection apparatus, so that changes in the relevant parameters will manifest as changes in the printed target. For example, the target pattern may be sensitive to chromatic aberrations in the lithographic projection apparatus (especially the projection system PL) as well as to the symmetry of the illumination, and the presence of such aberrations will manifest itself as a variation in the printed target pattern. Accordingly, scatterometry data of the printed target pattern is used to reconstruct the target pattern. Parameters of the target pattern, such as line width and shape, can be input into a reconstruction process carried out by the processing unit PU from knowledge of the printing steps and/or other scatterometry processes.

Although embodiments of scatterometers have been described herein, other types of metrology devices may be used in an embodiment. For example, a dark field measurement device such as that described in US Patent Application Publication No. 2013-0308142, which is hereby incorporated by reference in its entirety, may be used. Furthermore, those other types of metrology equipment may use entirely different techniques than scatterometry.

Figure 19 illustrates an exemplary composite metrology target formed on a substrate according to known practices. The composite target comprises four gratings 1932, 1933, 1934, 1935 positioned closely together so that they will all be within the measurement spot 1931 formed by the illumination beam of the metrology device. Thus, all four targets are simultaneously illuminated and imaged on the sensors 1904, 1918 simultaneously. In an example dedicated to overlay measurements, the gratings 1932, 1933, 1934, 1935 are themselves composite gratings formed from overlapping gratings patterned in different layers of the semiconductor device formed on the substrate. The gratings 1932, 1933, 1934, 1935 may have overlay offsets that are biased differently in order to facilitate overlay measurements between layers in which different portions of the composite grating are formed. The gratings 1932, 1933, 1934, 1935 may also differ in their orientation, as shown, so as to diffract incident radiation in the X and Y directions. In one example, gratings 1932 and 1934 are X-direction gratings with +d, -d offsets, respectively. This means that the grating 32 has its overlapping components arranged such that if they were both printed exactly in their nominal positions, one of the overlapping components would be offset by a distance d relative to the other. The grating 1934 has its components arranged so that if printed perfectly it would be an offset of d, but in the opposite direction to that of the first grating, and so on. Gratings 1933 and 1935 may be Y-direction gratings with offsets +d and -d, respectively. Although four gratings are shown, another embodiment may include a larger matrix to achieve the desired precision. For example, a 3x3 array of 9 composite gratings may have offsets -4d, -3d, -2d, -d, 0, +d, +2d, +3d, +4d. Individual images of these gratings can be identified in the images captured by the sensors 194,1918.

The metrology targets described herein may, for example, be overlay targets designed for use with metrology tools such as the Yieldstar stand-alone or integrated metrology tools, and/or alignment targets such as those commonly used in TwinScan lithography systems, Both of them are commercially available from ASML Corporation. In practice, the patterning device under test may include such a target that will itself generate a certain wavefront phase effect. More broadly, however, features on a patterning device, when illuminated by a scatterometer, will interact in a similar manner with the scatterometer's light, so that an understanding of the application of measurement to a metrology target applies equally to measuring patterning Other characteristics of the device.

In an embodiment, the radiation beam B is polarized. If the radiation beam is not polarized, the different polarizations that make up the radiation beam may reduce or cancel out the topography-induced focus differences of the patterning device such that no significant patterning-device topography-induced effects (e.g. poor focus). However, a polarized radiation beam may desirably be used, and if the radiation beam is polarized, this reduction or cancellation may not occur, and accordingly, the embodiments described herein may be used to reduce the shape of the patterning device. The effect introduced by appearance. Polarized radiation can be used in immersion lithography, so the embodiments described here may be advantageous for immersion lithography. The radiation beam of an EUV lithographic apparatus typically has an angle of eg about 6 degrees to its chief ray, and thus different polarization states provide different contributions to the radiation beam. Thus, the reflected beam is different for the two polarization directions and can also be considered polarized (at least to some extent). Embodiments of the invention may thus be advantageously used in EUV lithography.

In an embodiment, the patterning means may be provided with a functional pattern (a pattern that is to form part of the operating means). Alternatively or additionally, the patterning device may be provided with a measurement pattern which does not form part of the functional pattern. The measurement pattern can eg be located on one side of the functional pattern. This measurement pattern may eg be used to measure the alignment of the patterning device relative to the substrate table WT (see Fig. 1) of the lithographic apparatus or may be used to measure some other parameter (eg overlay). The techniques described here can be applied to such measurement patterns. Thus, for example, in an embodiment, the absorbent material used to form the measurement pattern may be the same or different than the absorbent material used to form the functional pattern. As another example, the absorbing material of the measurement pattern may be a material providing substantially complete absorption of the radiation beam. As another example, the absorbing material used to form the measurement pattern may be provided with a different thickness than the absorbing material used to form the functional pattern.

For aerial images, the contrast discussed here includes Image Log Slope (ILS) and/or Normalized Image Log Slope (NILS), while for resists, the contrast discussed here includes dose sensitivity and/or exposure Tolerance.

Although at times in the specification only the topography-induced phase of the patterning device (wavefront phase) may be discussed, it should be understood that such references may include use of the patterning device's topography-induced intensity (wavefront strength). Similarly, where only the topography-induced intensity of the patterning device (wavefront strength) may be discussed, it should be understood that such references may include the use of the topography-induced phase of the patterning device (wavefront phase).

As used herein, the terms "optimizing", "optimizing", and "optimizing" mean adjusting lithographic process parameters such that the lithographic process and/or results have more desirable characteristics, e.g., on a substrate Higher accuracy of projected design layouts, larger process windows, and more.

Embodiments of the invention may take the form of a computer program comprising one or more sequences of machine-readable instructions describing the methods as disclosed herein; or a data storage medium (e.g., semiconductor memory, magnetic or optical disk), in which Such a computer program is stored. Furthermore, computer readable instructions may be embodied in two or more computer programs. The two or more computer programs may be stored on one or more different memories and/or data storage media.

The computer program may eg be comprised by or in the imaging device of FIG. 1 and/or by or in the control unit LACU of FIG. 2 . Where an existing device (such as an example of the type shown in FIGS. 1-2 ) is already in production and/or in use, an embodiment may provide a method for causing a processor of the device to perform the methods described herein. Implemented by an updated computer program product.

Any of the controllers described herein may be operable, individually or in combination, when one or more computer programs are read by one or more computer processors located within at least one component of a lithographic apparatus. The controllers may have any suitable configuration for receiving, processing and sending signals, individually or in combination. The one or more processors are configured to communicate with at least one of the controllers. For example, each controller may include one or more processors for executing a computer program including computer readable instructions for the methods described above. A controller may include a data storage medium for storing such a computer program, and/or hardware for receiving such a medium. Accordingly, the controller may operate in accordance with the computer readable instructions of one or more computer programs.

Although specific references have been made above, using the described embodiments in the context of lithography using radiation, it will be appreciated that embodiments of the invention may be used in other applications, such as imprint lithography, and Lithography using radiation is not limited, as the case may be. In imprint lithography, the topography in the patterning device defines the pattern produced on the substrate. The topography of the patterning device may be printed into a resist layer provided to the substrate whereupon the resist is cured by application of electromagnetic radiation, heat, pressure or a combination thereof. After the resist has cured, the patterning device is removed from the resist, leaving a pattern in the resist.

Furthermore, although specific reference may be made herein to lithographic apparatus for fabricating integrated circuits (ICs), it should be understood that the lithographic apparatus described herein may have other applications, such as fabricating integrated optical systems, Guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCD), thin film magnetic heads, etc. Those skilled in the art will appreciate that, in the context of these alternative applications, any term "wafer" or "die" used herein may be considered synonymous with the more general term "substrate" or "target portion", respectively. of. The substrate referred to herein may be processed before or after exposure, for example in a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), by amount test tool and/or inspection tool. Where appropriate, the disclosure herein can be applied to these and other substrate processing tools. Furthermore, the substrate may be processed more than once, for example in order to produce a multilayer integrated circuit, so that the term substrate as used herein may also denote a substrate which already contains a plurality of processed layers.

The invention can also be described using the following aspects:

1. A method, said method comprising:

measuring the three-dimensional topography of a feature of a pattern of a lithographic patterning device; and

Wavefront phase information resulting from the three-dimensional topography of the pattern is calculated from the measurements.

2. The method according to aspect 1, further comprising calculating wavefront intensity information resulting from the three-dimensional topography of the pattern from the measurement results.

3. The method according to any one of aspects 1 to 2, wherein measuring the three-dimensional topography comprises measuring a feature selected from the group consisting of: critical dimension, pitch, side wall angle, absorber height, refractive index, Extinction coefficient, stacking order of absorbers and their combination.

4. The method according to any one of aspects 1 to 3, further comprising:

The measured three-dimensional topography of features of a pattern of the lithographic patterning device is used to determine a set of adjustments to adjustable parameters of a lithographic system in which the patterning device is used.

5. The method of aspect 4, further comprising using the patterning device and the adapted lithography system to image the pattern onto the radiation sensitive material disposed on the substrate.

6. The method of any one of aspects 1 to 5, wherein the measured three-dimensional topography of features of the pattern of the lithographic patterning device is used to simulate wavefront phase information of the lithographic system.

7. The method according to any one of clauses 1 to 6, wherein the calculated wavefront phase information is characterized by or is characterized by Zernike information.

8. The method of any one of clauses 1 to 6, wherein the calculated wavefront phase information is characterized by one of a Bessel function, a Jones matrix and a Muller matrix.

9. The method according to any one of aspects 1 to 8, wherein the measuring step comprises measuring with a scatterometer.

10. The method according to any one of aspects 1 to 9, wherein the measuring step comprises measuring with a scanning electron microscope or an atomic force microscope.

11. The method according to any one of aspects 1 to 9, wherein the measuring step comprises measuring using an optical metrology tool.

12. The method according to any one of aspects 1 to 9, wherein the measuring step comprises measuring with a scatterometer and the calculating step comprises a method selected from the group consisting of modeling three-dimensional topography , comparison of measured spectra with spectral libraries and iterative searches.

13. The method of any one of clauses 1 to 12, wherein calculating wavefront phase information is based on a diffraction pattern associated with an illumination profile of the lithographic apparatus.

14. The method of any one of clauses 1 to 12, wherein calculating optical wavefront phase information includes strictly calculating wavefront phase information.

15. The method of any one of clauses 1 to 14, wherein the wavefront phase information comprises wavefront phase information for a plurality of critical dimensions of the pattern.

16. The method according to any one of clauses 1 to 15, wherein the wavefront phase information comprises wavefront phase information for sidewall angles of the pattern and/or multiple angles of incidence of the illuminating radiation.

17. The method of any one of clauses 1 to 16, wherein the wavefront phase information comprises wavefront phase information for a plurality of pitches of the pattern.

18. The method of any one of clauses 1 to 17, wherein the wavefront phase information comprises wavefront phase information for a plurality of pupil positions or diffraction orders.

19. The method of any one of aspects 1 to 18, wherein calculating an imaging effect of the topography of the patterning device comprises calculating a simulated image of the pattern of the patterning device.

20. The method of any one of aspects 1 to 19, further comprising using the lithographic patterning apparatus to adjust parameters associated with the lithographic process to obtain an improvement in the contrast of the imaging of the pattern.

21. The method of aspect 20, wherein the parameter is a parameter of the topography of a pattern of the patterning device or a parameter of the illumination of the patterning device.

22. The method according to any one of aspects 1 to 21, comprising adjusting the refractive index of the patterning device, the extinction coefficient of the patterning device, the side wall angle of the absorber of the patterning device, the Height or thickness or any combination selected therefrom to minimize phase change.

23. A method according to any one of clauses 1 to 22, wherein the calculated wavefront phase information comprises an odd phase distribution across diffraction orders or a mathematical description thereof.

24. A non-volatile computer program product comprising machine readable instructions configured to cause a processor to perform the method according to any one of aspects 1 to 23.

25. A method of fabricating a device, wherein a lithographic process is used to apply a device pattern to a series of substrates, the method comprising using a method according to any one of aspects 1 to 23 to determine the availability of a lithographic system. The parameters are adjusted and the device pattern is exposed onto the substrate.

The patterning devices described herein may be referred to as photolithographic patterning devices. Thus, the term "lithographic patterning device" may be interpreted to mean a patterning device suitable for use in a lithographic apparatus.

The terms "radiation" and "beam" as used herein include all types of electromagnetic radiation, including: ultraviolet radiation (UV) (e.g. having a wavelength at or about 365, 355, 248, 193, 157 or 126 nm) and extreme ultraviolet (EUV ) radiation (for example having a wavelength in the range of 5-20 nm), and particle beams, such as ion beams or electron beams.

Where the context allows, the term "lens" may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic, and electrostatic optical components.

References to "embodiments," "example," etc. in the described embodiments and the specification indicate that the embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include specific features, structures, or features. or characteristics. Additionally, such terms are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure or characteristic is described in conjunction with an embodiment, it is to be understood that implementing such feature, structure or characteristic as well as other embodiments are within the knowledge of those skilled in the art whether or not explicitly described.

The foregoing description is intended to be illustrative rather than limiting. Accordingly, it will be apparent to those skilled in the art that changes may be made in the invention as described without departing from the scope of the claims hereinafter set forth. For example, one or more aspects of one or more embodiments may be combined with, or substituted for, one or more aspects of one or more other embodiments, as appropriate. Therefore, such modifications and adaptations are intended to be within the range and meaning of equivalents of the disclosed embodiments, based on the teaching and suggestion presented herein. It should be understood that the terms or expressions herein are for the purpose of exemplification and description rather than limitation, so that the terms or expressions in this specification can be interpreted by those skilled in the art according to the teaching and inspiration. The coverage and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents.

Claims (15)

1. a kind of method, methods described includes：

Measure the three-dimensional appearance of the feature of the pattern of photoengraving pattern forming apparatus；With

Wavefront phase information caused by the three-dimensional appearance of pattern is calculated according to measurement result.

2. according to the method described in claim 1, in addition to according to measurement result calculate caused by the three-dimensional appearance of pattern Wavefront strength information.

3. according to the method described in claim 1, wherein measurement three-dimensional appearance includes measurement selected from the group being made up of following features Feature：Critical dimension, pitch, side wall angle, absorber height, refractive index, extinction coefficient, absorber stack order and its group Close.

4. according to the method described in claim 1, in addition to：

Determined using the three-dimensional appearance measured by the feature of the pattern of photoengraving pattern forming apparatus for patterning device One group of adjustment amount of the customized parameter for the etching system being used in.

5. method according to claim 4, will also scheme including the use of patterning device and the etching system adjusted Case is imaged onto on the radiation-sensitive materials being arranged on substrate.

6. according to the method described in claim 1, the wherein measured three-dimensional of the feature of the pattern of photoengraving pattern forming apparatus Pattern is used for the wavefront phase information for simulating etching system.

7. according to the method described in claim 1, wherein the measuring process is included with scatterometer and/or SEM Or AFM and/or optical measurement tools are measured.

8. according to the method described in claim 1, wherein the measuring process includes measuring with scatterometer, and the calculating Step includes the method in the group selected from following methods composition：Three-dimensional appearance is modeled, by measured spectrum and library of spectra It is compared and iterative search.

9. according to the method described in claim 1, wherein it is based on the illumination profile with lithographic equipment to calculate wavefront phase information Associated diffraction pattern.

10. according to the method described in claim 1, wherein wavefront phase information includes the ripple of multiple critical dimensions for pattern Preceding phase information, and/or side wall angle and/or the wavefront phase information of multiple incidence angles of illumination radiation for pattern, and/or For the wavefront phase information, and/or the wavefront phase information for multiple pupil locations or the order of diffraction of multiple pitches of pattern.

11. according to the method described in claim 1, also adjust related to photoetching process including the use of photoengraving pattern forming apparatus The parameter of connection obtains the improvement of the contrast of the imaging of pattern.

12. method according to claim 11, wherein the parameter is the parameter of the pattern of the pattern of patterning device Or the parameter of the irradiation of patterning device.

13. according to the method described in claim 1, including the regulation refractive index of patterning device, patterning device disappear Backscatter extinction logarithmic ratio, the side wall angle of the absorber of patterning device, the height of the absorber of patterning device or thickness or from its Any combination of middle selection, to minimize phase place change.

14. a kind of non-volatile computer program product, including be configured to make computing device side according to claim 1 The machine readable instructions of method.

15. a kind of method for manufacturing device, wherein being applied device pattern to a series of substrate, the side using photoetching process Method determines the customized parameter of etching system including the use of method according to claim 1 and the device pattern is exposed into lining On bottom.